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How to find String length in java with and without string method

Get String length with String length() method

To find String length in java there is a method length().

This method is used to get length of string.

Signature of length method is:

public int length()

1	public int length()

Length method returns the length of the string. it counts the number of unicode in string.

public class MyClass {
    public static void main(String args[]) {
     String text="Hello How are you";
     int length=text.length();
     System.out.println("Length of string "+length);
    
    }
}

public class MyClass {

public static void main(String args[]) {

String text="Hello How are you";

int length=text.length();

System.out.println("Length of string "+length);

}

This is very simple way to get length of a string in java.

Output

Length of string 17

1	Length of string 17

Finding the length of unicode string in java

Here we are considering hindi language stored in String. We use length() to get the string length.

You can take any unicode character to check length string length() works properly.

public class StringLength {
    public static void main(String args[]) {
        String text = "उठो, जागो और तब तक मत रुको जब तक लक्ष्य की प्राप्ति ना हो जाये।";
        int length = text.length();
        System.out.println("Length of string " + length);
    }
}

public class StringLength {

public static void main(String args[]) {

String text = "उठो, जागो और तब तक मत रुको जब तक लक्ष्य की प्राप्ति ना हो जाये।";

int length = text.length();

System.out.println("Length of string " + length);

}

Output

Length of string 63

1	Length of string 63

Finding the String length in java of unicode characters

Here we have stored a unicode value in String and finding its length.

public class StringLength {
    public static void main(String args[]) {
        String text = "\u0041";
        int length = text.length();
        System.out.println("Length of string " + length);
         System.out.println("unicode character is  " + text);
    }
}

public class StringLength {

public static void main(String args[]) {

String text = "\u0041";

int length = text.length();

System.out.println("Length of string " + length);

System.out.println("unicode character is " + text);

}

Output

Length of string 1
unicode character is  A

1 2	Length of string 1 unicode character is A

Using toCharArray() to find String length in java

toCharArray() is another method in String class to convert String to character array.

Signature of toCharArray() is

public char[] toCharArray()

1	public char[] toCharArray()

public class CharArrayLength {
    public static void main(String[] args) {
        String text = "When our false perception is corrected, misery ends also";
        char[] charArray = text.toCharArray();
        int length = charArray.length;
        System.out.println("Length of text is " + length);
    }
}

public class CharArrayLength {

public static void main(String[] args) {

String text = "When our false perception is corrected, misery ends also";

char[] charArray = text.toCharArray();

int length = charArray.length;

System.out.println("Length of text is " + length);

}

In above program String is converted to character array using toCharArray().

Character array is have a field length. This length property finds the length of character array.

Output

Length of text is 56

1	Length of text is 56

Using Function to find the String length in java

In above program you find length of Java String in main method.

Here we have created two static methods length() and length1().

these two methods are accepting string and getting its length.

public class StringLenghtForLoop {
    public static int length(String s) {
        return s.length();
    }
     public static int length1(String s) {
       return s.toCharArray().length;
    }
    public static void main(String[] args) {
        String text = "Hello How are you";
        int length = length(text);
        System.out.println("String length is " + length);
        int length1 = length1(text);
        System.out.println("String length is " + length1);
    }
}

public class StringLenghtForLoop {

public static int length(String s) {

return s.length();

}

public static int length1(String s) {

return s.toCharArray().length;

}

public static void main(String[] args) {

String text = "Hello How are you";

int length = length(text);

System.out.println("String length is " + length);

int length1 = length1(text);

System.out.println("String length is " + length1);

}

Using Recursion to find String length

Here we are using recursion to find the length of string.

When a function is called it is checking the lenth of string if string is empty then return zero else call again itself with adding one to return value.

On each recursive call we are eliminating first character from string.

public class StringLenght {

    public static int length(String s) {
        if (s.isEmpty()) {
            return 0;
        } else {
            return length(s.substring(1))+1;
        }
    }
    public static void main(String[] args) {
        String text = "Hello How are you";
        int length = length(text);
        System.out.println("String length is " + length);
    }
}

public class StringLenght {

public static int length(String s) {

if (s.isEmpty()) {

return 0;

} else {

return length(s.substring(1))+1;

}

public static void main(String[] args) {

String text = "Hello How are you";

int length = length(text);

System.out.println("String length is " + length);

}

Output

String length is 17

1	String length is 17

Hope you learn and understand how to get length of string as we discussed different ways to find string length.

Keep Reading other topics.

Inheritance in Java-Types and Examples

Inheritance in Java is the process of acquiring the properties of one class object into another class object.

It allows the hierarchical classification. Inheritance also provides the facility of reusability.

In Java programming, a class that is inherited is called a superclass or sub class or parent class and class that does the inheriting is called sub class or child class.

If we want to inherit a class, we simply incorporate the definition of one class into another class by using extends keyword.

General form of a class declaration that inherits a super class

class  subClass <strong>extends </strong>  superClass{ 
 <br>
  }

class subClass <strong>extends </strong> superClass{

<br>

}

Type of Inheritance in Java

There are following type of inheritance

Single level Inheritance
Multi-level Inheritance
Hierarchical Inheritance
Hybrid Inheritance

Note: Java does not support multiple inheritance.

Single level Inheritance

Property of single level inheritance is as below

One Super class and one sub class
Sub class inherits the features of super class

Write a program for single level inheritance.

class Parent // create a super class	
{	
    int  x ,y;
    void showA()
    {       
        System.out.println("x="  +x+" y=" + y); 
    }		
   }


class Child extends Parent // create a sub class	
{	
    int  z; 
    void showB()
    {   
        System.out.println("x="  +x + "  y=" + y + " z=" +z );
    }
/* in sub class, member of super class can be accessed directly without any object. */                     }


public class Test {

    public static void main(String arg[]) {
        Child obj = new Child();
        obj.x = 10;	// subclass has access to all public members of its super class	
        obj.y =  20;	// subclass has access to all public members of its super class	
        obj.showA();	// subclass has access to all public members of its super class	
        obj.z = 30;
        obj.showB();
    }
}

class Parent // create a super class

{

int x ,y;

void showA()

{

System.out.println("x=" +x+" y=" + y);

}

class Child extends Parent // create a sub class

{

int z;

void showB()

{

System.out.println("x=" +x + " y=" + y + " z=" +z );

}

/* in sub class, member of super class can be accessed directly without any object. */ }

public class Test {

public static void main(String arg[]) {

Child obj = new Child();

obj.x = 10; // subclass has access to all public members of its super class

obj.y = 20; // subclass has access to all public members of its super class

obj.showA(); // subclass has access to all public members of its super class

obj.z = 30;

obj.showB();

}

Multi level Inheritance

In multi level inheritance inheritance exists in multiple level.

One Super Class
It has a child class
Child class has a child class

This process may continue and each child class inherits feature of all parent class.

program for Multi level inheritance.

class A { 

    int x;

}

class B extends A {

    int y;
}

class C extends B {

    int z;

    void show() {
        System.out.println("x=" + x + "  y=" + y + " z=" + z);
        /* in sub class, member of super class can be accessed directly without any object. */

    }
}

public class Test {

    public static void main(String arg[]) {
        C objC = new C();
        objC.x = 10;	// subclass has access to all public members of its super class
        objC.y = 20;	// subclass has access to all public members of its super class
        objC.z = 30;
        objC.show();	// subclass has access to all public members of its super class	
    }
}

class A {

int x;

}

class B extends A {

int y;

}

class C extends B {

int z;

void show() {

System.out.println("x=" + x + " y=" + y + " z=" + z);

/* in sub class, member of super class can be accessed directly without any object. */

}

public class Test {

public static void main(String arg[]) {

C objC = new C();

objC.x = 10; // subclass has access to all public members of its super class

objC.y = 20; // subclass has access to all public members of its super class

objC.z = 30;

objC.show(); // subclass has access to all public members of its super class

}

Result

x=10  y=20 z=30

1	x=10 y=20 z=30

Hierarchical Inheritance

Hybrid Inheritance

<strong></strong>

1	<strong></strong>

Result

x=10 y=20
x=10  y=20 z=30

1 2	x=10 y=20 x=10 y=20 z=30

Note: A subclass can access the public member of super class. A subclass can’t access the private member of super class.

Super Class Cant Access Sub Class Member

A sub class can access all the public member of super class but reverse is not true. Super class cannot access sub class data.

class Parent // create a super class	
{

    int x;

    void showParent() {
        System.out.println("x =" + x + "  y=" + y);
        /* error, y cant be accessed here, because y is a member of sub class. */
    }
}

class Child extends Parent // create a sub class
{

    int y;

    void showChild() {
         System.out.println("x =" + x + "  y=" + y);
    }
    /* in sub class, member of super class can be accessed directly without any object. */
}

public class TestInheritance {

    public static void main(String arg[]) {
        Child obj = new Child();
        obj.x = 10;	// subclass has access to all public members of its super class	
        obj.y = 20;	// subclass has access to all public members of its super class
        obj.showParent();	// subclass has access to all public members of its super class	
        obj.showChild();
    }
}

class Parent // create a super class

{

int x;

void showParent() {

System.out.println("x =" + x + " y=" + y);

/* error, y cant be accessed here, because y is a member of sub class. */

}

class Child extends Parent // create a sub class

{

int y;

void showChild() {

System.out.println("x =" + x + " y=" + y);

}

/* in sub class, member of super class can be accessed directly without any object. */

}

public class TestInheritance {

public static void main(String arg[]) {

Child obj = new Child();

obj.x = 10; // subclass has access to all public members of its super class

obj.y = 20; // subclass has access to all public members of its super class

obj.showParent(); // subclass has access to all public members of its super class

obj.showChild();

}

Result

error: cannot find symbol
        System.out.println("x =" + x + "  y=" + y);
                                                ^
  symbol:   variable y
  location: class Parent
1 error

error: cannot find symbol

System.out.println("x =" + x + " y=" + y);

symbol: variable y

location: class Parent

1 error

A sub class can’t access the private member of super class.

class A { // super class	

    private int x;
}

class B extends A {// sub class	

    int y;

    void showB() {
        System.out.println("x & y =" + x + "    " + y); //error 
        /*  sub class, can’t access private member its super class . */
    }

}

public class Test11 {

    public static void main(String args9[]) {
        B objB = new B();
        objB.showB();

    }
}

class A { // super class

private int x;

}

class B extends A {// sub class

int y;

void showB() {

System.out.println("x & y =" + x + " " + y); //error

/* sub class, can’t access private member its super class . */

}

public class Test11 {

public static void main(String args9[]) {

B objB = new B();

objB.showB();

}

Result

Test11.java:11: error: x has private access in A
        System.out.println("x=" + x + "   y=" + y); //error 
                                       ^
1 error

Test11.java:11: error: x has private access in A

System.out.println("x=" + x + " y=" + y); //error

1 error

Write a program for Hierarchical Inheritance.

class A {

    int x;
}

class B extends A {

    int y;

    void showB() {
        System.out.println("x=" + x + "  y=" + y);
        /* in sub class, member of super class can be accessed directly without any object. */
    }
}

class C extends A {

    int z;

    void showC() {
        System.out.println("x=" + x + "  z=" + z);
        /* in sub class, member of super class can be accessed directly without any object. */
    }
}

public class Test {

    public static void main(String arg[]) {
        B objB = new B();
        C objC = new C();
        objB.x = 10;	// subclass has access to all public members of its super class	
        objB.y = 20;	// subclass has access to all public members of its super class				
        objC.x = 100;	// subclass has access to all public members of its super class		
        objC.z = 200;	// subclass has access to all public members of its super class				
        objB.showB();	// subclass has access to all public members of its super class
        objC.showC();	// subclass has access to all public members of its super class	
    }
}

class A {

int x;

}

class B extends A {

int y;

void showB() {

System.out.println("x=" + x + " y=" + y);

/* in sub class, member of super class can be accessed directly without any object. */

}

class C extends A {

int z;

void showC() {

System.out.println("x=" + x + " z=" + z);

/* in sub class, member of super class can be accessed directly without any object. */

}

public class Test {

public static void main(String arg[]) {

B objB = new B();

C objC = new C();

objB.x = 10; // subclass has access to all public members of its super class

objB.y = 20; // subclass has access to all public members of its super class

objC.x = 100; // subclass has access to all public members of its super class

objC.z = 200; // subclass has access to all public members of its super class

objB.showB(); // subclass has access to all public members of its super class

objC.showC(); // subclass has access to all public members of its super class

}

Result

x=10  y=20
x=100  z=200

1 2	x=10 y=20 x=100 z=200

String in Java- Constructor methods and examples

Java String is defined in java.lang.String.

Java String is a sequence of characters quoted in double quote (” “).

String Constructors

Java String Methods

There are many methods avaible in string class few common and widely used methods are

Java String Method charAt()

This method takes one integer argument and return a character specified at index position.

For any string the index value starts from 0 to string length -1 position.

If passed index value not in valid range then it throws IndexOutOfBoundsException.

For example string Hello Friends contains 13 characters starting from 0 to 12 H is first position with index value 0, F is in seventh position with index value 6 and s is in 13 position with index value 12.

Using number other then 0 to 12( 0 to length()-1) will result in IndexOutOfBountException

Signature:

public char charAt(int index)

Parameters:

index -Integer index value to get character at specified index position.

Return:

Character at passed index value.

Exception Throws:

IndexOutOfBoundsException If index value in not between 0 to String length()-1

Example

public class StringChatAtExample {

    public static void main(String args[]) {
        String test = "Java String charAt() example";
        char firstCharacter = test.charAt(0);
        char sixthCharacter = test.charAt(5);
        char lastCharacter = test.charAt(test.length() - 1);
        System.out.println("String:" + test);
        System.out.println("Character at first position: " + firstCharacter);
        System.out.println("Character at sixth position: " + sixthCharacter);
        System.out.println("Character at last position: " + lastCharacter);
    }

}

Sr No	Constructor and description
1	String() Create a new empty string object
2	String(byte[] bytes) Construct a string object with byte array
3	String(char[] value) Construct a string object with character array
4	String(String original) Create a string with another string
5	String(StringBuffer buffer) Create a string with StringBuffer object
6	String(StringBuilder builder) Create a string with StringBuilder object

public class StringChatAtExample {

public static void main(String args[]) {

String test = "Java String charAt() example";

char firstCharacter = test.charAt(0);

char sixthCharacter = test.charAt(5);

char lastCharacter = test.charAt(test.length() - 1);

System.out.println("String:" + test);

System.out.println("Character at first position: " + firstCharacter);

System.out.println("Character at sixth position: " + sixthCharacter);

System.out.println("Character at last position: " + lastCharacter);

}

Result

String:Java String charAt() example
Character at first position: J
Character at sixth position: S
Character at last position: e

String:Java String charAt() example

Character at first position: J

Character at sixth position: S

Character at last position: e

Now Print all characters with its index value

Example

public class StringChatAtExample1 {
    public static void main(String args[]) {
        String test = "Java String charAt() example";
       for(int i=0;i&lt;=test.length()-1;i++){
           System.out.println("Character at  index value "+i+" = "+test.charAt(i));
       }
    }

}

public class StringChatAtExample1 {

public static void main(String args[]) {

String test = "Java String charAt() example";

for(int i=0;i<=test.length()-1;i++){

System.out.println("Character at index value "+i+" = "+test.charAt(i));

}

Result

Character at  index value 0 = J
Character at  index value 1 = a
Character at  index value 2 = v
Character at  index value 3 = a
Character at  index value 4 =  
Character at  index value 5 = S
Character at  index value 6 = t
Character at  index value 7 = r
Character at  index value 8 = i
Character at  index value 9 = n
Character at  index value 10 = g
Character at  index value 11 =  
Character at  index value 12 = c
Character at  index value 13 = h
Character at  index value 14 = a
Character at  index value 15 = r
Character at  index value 16 = A
Character at  index value 17 = t
Character at  index value 18 = (
Character at  index value 19 = )
Character at  index value 20 =  
Character at  index value 21 = e
Character at  index value 22 = x
Character at  index value 23 = a
Character at  index value 24 = m
Character at  index value 25 = p
Character at  index value 26 = l
Character at  index value 27 = e

Character at index value 0 = J

Character at index value 1 = a

Character at index value 2 = v

Character at index value 3 = a

Character at index value 4 =

Character at index value 5 = S

Character at index value 6 = t

Character at index value 7 = r

Character at index value 8 = i

Character at index value 9 = n

Character at index value 10 = g

Character at index value 11 =

Character at index value 12 = c

Character at index value 13 = h

Character at index value 14 = a

Character at index value 15 = r

Character at index value 16 = A

Character at index value 17 = t

Character at index value 18 = (

Character at index value 19 = )

Character at index value 20 =

Character at index value 21 = e

Character at index value 22 = x

Character at index value 23 = a

Character at index value 24 = m

Character at index value 25 = p

Character at index value 26 = l

Character at index value 27 = e

Java String Method compareToIgnoreCase()

This method is used to compare two string with case ignorance and compare both string lexicographically. If both strings are same then it returns 0. If first string is greater then another then it returns positive integer, if second string is greater then first then it returns negative integer value.

Signature

public int compareToIgnoreCase(String str)

Parameters

str – String value that will compared with string.

Return

Integer value. if string is greater then passed str value then it returns positive integer if both strings are equal then it returns zero if passed str is greater then string then this method returns negative integer value.

Example1

    public class StringCompare1 {

    public static void main(String[] args) {

        System.out.println("Comparing A with A " + "A".compareToIgnoreCase("A"));
        System.out.println("Comparing A with b " + "A".compareToIgnoreCase("b"));
        System.out.println("Comparing C with b " + "C".compareToIgnoreCase("b"));
        System.out.println("Comparing A with Z " + "A".compareToIgnoreCase("Z"));
        System.out.println("Comparing Z with A " + "Z".compareToIgnoreCase("A"));
    }
}

public class StringCompare1 {

public static void main(String[] args) {

System.out.println("Comparing A with A " + "A".compareToIgnoreCase("A"));

System.out.println("Comparing A with b " + "A".compareToIgnoreCase("b"));

System.out.println("Comparing C with b " + "C".compareToIgnoreCase("b"));

System.out.println("Comparing A with Z " + "A".compareToIgnoreCase("Z"));

System.out.println("Comparing Z with A " + "Z".compareToIgnoreCase("A"));

}

Result

Comparing A with A 0
Comparing A with b -1
Comparing C with b 1
Comparing A with Z -25
Comparing Z with A 25

Comparing A with A 0

Comparing A with b -1

Comparing C with b 1

Comparing A with Z -25

Comparing Z with A 25

In above program comparing same string is returning 0. In second println() statement A is lexicographically smaller then b so it is returning -1. In third println() statement C is lexicographically greater then b so it is returning 1 and so on.

Example2

public class StringCompare {

    public static void main(String[] args) {
        String first = "Hello";
        String second = "Hell";
        String third = "Bye";
        String fourth = "hello";
        String fifth = "Hello";
        String sixth = "xyz";
        int result1 = first.compareToIgnoreCase(second);
        System.out.println("result1 " + result1);
        int result2 = first.compareToIgnoreCase(third);
        System.out.println("result2 " + result2);
        int result3 = first.compareToIgnoreCase(fourth);
        System.out.println("result3 " + result3);
        int result4 = first.compareToIgnoreCase(fifth);
        System.out.println("result4 " + result4);
        int result5 = first.compareToIgnoreCase(sixth);
        System.out.println("result5 " + result5);
    }
}

public class StringCompare {

public static void main(String[] args) {

String first = "Hello";

String second = "Hell";

String third = "Bye";

String fourth = "hello";

String fifth = "Hello";

String sixth = "xyz";

int result1 = first.compareToIgnoreCase(second);

System.out.println("result1 " + result1);

int result2 = first.compareToIgnoreCase(third);

System.out.println("result2 " + result2);

int result3 = first.compareToIgnoreCase(fourth);

System.out.println("result3 " + result3);

int result4 = first.compareToIgnoreCase(fifth);

System.out.println("result4 " + result4);

int result5 = first.compareToIgnoreCase(sixth);

System.out.println("result5 " + result5);

}

Result

result1 1
result2 6
result3 0
result4 0
result5 -16

result1 1

result2 6

result3 0

result4 0

result5 -16

Java String Method indexOf with int parameter

indexOf(int ch) method is used to get the first occurrence of a character in given string. This method takes a character input (in Unicode code units) and return the index value of character in string, if character not found in string then it returns -1.

Signature

public int indexOf(int ch)

Parameters

A charcter value in unicode code point.

Return

Returns the int value that represents the first occurance of the character in string, if character not fount in string then it returns -1.

Example

public class StringIndexOf1 {

    public static void main(String[] args) {
        String string = "Java is a Object Oriented Programming Language";
        System.out.println("Index of Character J is " + string.indexOf('J'));
        System.out.println("Index of Character J is " + string.indexOf(0x4A));
        System.out.println("Index of Character O is " + string.indexOf('O'));
        System.out.println("Index of Character e is " + string.indexOf('e'));
        System.out.println("Index of Character E is " + string.indexOf('E'));
        System.out.println("Index of Character z is " + string.indexOf('z'));
    }
}

public class StringIndexOf1 {

public static void main(String[] args) {

String string = "Java is a Object Oriented Programming Language";

System.out.println("Index of Character J is " + string.indexOf('J'));

System.out.println("Index of Character J is " + string.indexOf(0x4A));

System.out.println("Index of Character O is " + string.indexOf('O'));

System.out.println("Index of Character e is " + string.indexOf('e'));

System.out.println("Index of Character E is " + string.indexOf('E'));

System.out.println("Index of Character z is " + string.indexOf('z'));

}

Index of Character J is 0
Index of Character J is 0
Index of Character O is 10
Index of Character e is 13
Index of Character E is -1
Index of Character z is -1

Index of Character J is 0

Index of Character O is 10

Index of Character e is 13

Index of Character E is -1

Index of Character z is -1

Java String Method indexOf()

indexOf method is used to get the first occurrence of a sub string in given string. This method takes a string input and return the index value of it in given string object, if sub string not found in string then it returns -1.

Signature

public int indexOf(String str)

Parameters

str is sub string value to find in specified string.

Return

Returns the int value that represents the first occurrence of the sub string in string, if sub string not fount in string then it returns -1.

Example

public class StringIndexOfExample {
    public static void main(String[] args) {
        String text = "World is beautiful";
        System.out.println("Index of w is " + text.indexOf("w"));
        System.out.println("Index of W is " + text.indexOf("W"));
        System.out.println("Index of i is " + text.indexOf("i"));
        System.out.println("Index of l is " + text.indexOf("l"));
        System.out.println("Index of world is " + text.indexOf("world"));
        System.out.println("Index of World is " + text.indexOf("World"));
        System.out.println("Index of is is " + text.indexOf("is"));
        System.out.println("Index of beautiful is " + text.indexOf("beautiful"));
    }

}

public class StringIndexOfExample {

public static void main(String[] args) {

String text = "World is beautiful";

System.out.println("Index of w is " + text.indexOf("w"));

System.out.println("Index of W is " + text.indexOf("W"));

System.out.println("Index of i is " + text.indexOf("i"));

System.out.println("Index of l is " + text.indexOf("l"));

System.out.println("Index of world is " + text.indexOf("world"));

System.out.println("Index of World is " + text.indexOf("World"));

System.out.println("Index of is is " + text.indexOf("is"));

System.out.println("Index of beautiful is " + text.indexOf("beautiful"));

}

Result

Index of w is -1
Index of W is 0
Index of i is 6
Index of l is 3
Index of world is -1
Index of World is 0
Index of is is 6
Index of beautiful is 9

Index of w is -1

Index of W is 0

Index of i is 6

Index of l is 3

Index of world is -1

Index of World is 0

Index of is is 6

Index of beautiful is 9

Java String Method lastIndexOf

This method take a string parameter as input and return the last index value of parameter string in specified string. If string not found then it returns -1.
The second overloaded method find the string from fromindex position.

Signature

public int lastIndexOf(String str)
public int lastIndexOf(String str, int fromIndex)

Parameters

str- to search in String
fromindex- to search str from specified index

Return

Return the last index value of parameter str in specified string. If str not found then it returns -1

Example

public class StringLastIndexOf {

    public static void main(String[] args) {
        String s = "People who practice a lot get higher scores.";
        System.out.println("Last index of a :" + s.lastIndexOf("a"));
        System.out.println("Last index of J :" + s.lastIndexOf("J"));
        System.out.println("Last index of s :" + s.lastIndexOf("s"));
        System.out.println("Last index of lot :" + s.lastIndexOf("lot"));
    }

}

public class StringLastIndexOf {

public static void main(String[] args) {

String s = "People who practice a lot get higher scores.";

System.out.println("Last index of a :" + s.lastIndexOf("a"));

System.out.println("Last index of J :" + s.lastIndexOf("J"));

System.out.println("Last index of s :" + s.lastIndexOf("s"));

System.out.println("Last index of lot :" + s.lastIndexOf("lot"));

}

Result

Last index of a :20
Last index of J :-1
Last index of s :42
Last index of lot :22

Last index of a :20

Last index of J :-1

Last index of s :42

Last index of lot :22

Java String substring() method

This method takes a int argument to generate sub string of string. It returns sub string starting from beginIndex value to last of string.
The second overloaded method allows to specify the ending index value also.
beginIndex parameters is inclusive and endIndex is exclusive.

Signature

public String substring(int beginIndex)
public String substring(int beginIndex,int endIndex)

Parameters

beginIndex –generate substring from this index value(inclusive).
endIndex-generate substring up to endIndex-1 value(exclusive).

Return

A substring

Throw

IndexOutOfBoundsException: If beginIndex is negative or endIndex is greater then length of string or if beginIndex is greater then endIndex.

Example

public class StringSubString {

    public static void main(String[] args) {
        String str = "It is very simple to be happy";
        System.out.println("Substring1  : " + str.substring(0));
        System.out.println("Substring2  : " + str.substring(6));
        System.out.println("Substring3  : " + str.substring(18));
        System.out.println("Substring4  : " + str.substring(24));
        System.out.println("Substring5  : " + str.substring(0, 17));
        System.out.println("Substring6  : " + str.substring(21, str.length()));
    }
}

public class StringSubString {

public static void main(String[] args) {

String str = "It is very simple to be happy";

System.out.println("Substring1 : " + str.substring(0));

System.out.println("Substring2 : " + str.substring(6));

System.out.println("Substring3 : " + str.substring(18));

System.out.println("Substring4 : " + str.substring(24));

System.out.println("Substring5 : " + str.substring(0, 17));

System.out.println("Substring6 : " + str.substring(21, str.length()));

}

Result

Substring1  : It is very simple to be happy
Substring2  : very simple to be happy
Substring3  : to be happy
Substring4  : happy
Substring5  : It is very simple
Substring6  : be happy

Substring1 : It is very simple to be happy

Substring2 : very simple to be happy

Substring3 : to be happy

Substring4 : happy

Substring5 : It is very simple

Substring6 : be happy

Java String concat() method

String concat() is used to concatenate two strings. The parameter str string is appended to specified string and new string object is returned by this method.
Example
“Hello ”.concat(“Friends”)
This will generate a new string object “Hello Friends”

Parameters

Str – is string parameter used to concatenate with specified string

Example

public class StringConcat {

    public static void main(String[] args) {
        String str = "Hello Friends";
        String str1 = "How are you";
        String str3 = str.concat(" ").concat(str1);
        System.out.println(str3);
    }
}

public class StringConcat {

public static void main(String[] args) {

String str = "Hello Friends";

String str1 = "How are you";

String str3 = str.concat(" ").concat(str1);

System.out.println(str3);

}

Hello Friends How are you

1	Hello Friends How are you

Here str is concatenated with ” ” then it is concatenated with str1 and result is assigned to str3 String object.

Sr No	Constructor and Description
1	StringTokenizer(String str) Construct a string tokenizer for given string
2	StringTokenizer(String str, String delim) Construct a string tokenizer for given string and generate tokens based on delimiters
3	StringTokenizer(String str, String delim, boolean returnDelims) Construct a string tokenizer for given string and generate tokens based on delimiters the returnDelims specify whether to include delim in token or not

In a programming language we have to repeat set of instruction many time as per programmer’s requirements.

To repeat instructions java provides looping statements. Looping is also known as Iterative statement
Following are types of loop in java.
1. For loop statement
2. While loop statement
3. Do while loop statement
4. For each loop (enhanced for loop)

Work of above statement are same but the have syntax difference. Let us see all of them one by one

1 For Loop in Java

for loop syntax in java

for( initialization; conditionCheck;updating){
      Body of loop
   }

for( initialization; conditionCheck;updating){

Body of loop

}

Example: Print 1 to 10 numbers using for loop in java

public class ForStatement {
    public static void main(String[] args) {
        for (int i = 1; i &lt;= 10; i++) {
            System.out.println("Iteration number " + i);
        }
    }
}

public class ForStatement {

public static void main(String[] args) {

for (int i = 1; i <= 10; i++) {

System.out.println("Iteration number " + i);

}

In for statement first loop variable is initialized then condition is checked if condition is true body of loop is executed after that variable is updated.

Again condition is cheeked condition satisfied body of loop is executed and variable updated this process is continue until condition is false.

Variable initialization is done only once.

Output

Iteration number 1
Iteration number 2
Iteration number 3
Iteration number 4
Iteration number 5
Iteration number 6
Iteration number 7
Iteration number 8
Iteration number 9
Iteration number 10

Iteration number 1

Iteration number 2

Iteration number 3

Iteration number 4

Iteration number 5

Iteration number 6

Iteration number 7

Iteration number 8

Iteration number 9

Iteration number 10

2 While Loop in Java

while loop syntax in java

Initialization
While (condition){
Body of loop;
}

Initialization

While (condition){

Body of loop;

}

In while statement only condition is checked if condition is true then the body of loop is executed loop variable initialization should be before the while statement.

Variable updating is part of body of loop.

Example: Print 1 to 10 numbers using for loop in java

public class WhileStatement {

    public static void main(String[] args) {
        int i = 1;
        while (i <= 10) {
            System.out.println("Iteration Number " + i);
            i++;
        }
    }
}

public class WhileStatement {

public static void main(String[] args) {

int i = 1;

while (i <= 10) {

System.out.println("Iteration Number " + i);

i++;

}

Output

Iteration Number 1
Iteration Number 2
Iteration Number 3
Iteration Number 4
Iteration Number 5
Iteration Number 6
Iteration Number 7
Iteration Number 8
Iteration Number 9
Iteration Number 10

Iteration Number 1

Iteration Number 2

Iteration Number 3

Iteration Number 4

Iteration Number 5

Iteration Number 6

Iteration Number 7

Iteration Number 8

Iteration Number 9

Iteration Number 10

3 do while in Java

do while loop syntax in java

initialization;
do{
    Body of loop;
}while (condition);

initialization;

do{

Body of loop;

}while (condition);

In do loop condition is cheeked at last. First time body of loop is excuted without checking the condition after that if condition specified in while is true then body of loop is executed until condition is false.

Example: Print 1 to 10 numbers using for loop in java

public class DoWhileStatement {

    public static void main(String[] s) {
        int i = 1;
        do {
            System.out.println("Iteration Number " + i);
            i++;
        } while (i <= 10);
    }
}

public class DoWhileStatement {

public static void main(String[] s) {

int i = 1;

do {

System.out.println("Iteration Number " + i);

i++;

} while (i <= 10);

}

Result

Iteration Number 1
Iteration Number 2
Iteration Number 3
Iteration Number 4
Iteration Number 5
Iteration Number 6
Iteration Number 7
Iteration Number 8
Iteration Number 9
Iteration Number 10

Iteration Number 1

Iteration Number 2

Iteration Number 3

Iteration Number 4

Iteration Number 5

Iteration Number 6

Iteration Number 7

Iteration Number 8

Iteration Number 9

Iteration Number 10

If condition is false then also do while statement is executed once.
Example: Executing do while loop once in false condition.

public class DoWhileStatement1 {

    public static void main(String[] s) {
        int i = 20;
        do {
            System.out.println("Iteration Number " + i);
            i++;
        } while (i <= 10);
    }
}

public class DoWhileStatement1 {

public static void main(String[] s) {

int i = 20;

do {

System.out.println("Iteration Number " + i);

i++;

} while (i <= 10);

}

Result

Iteration Number 20

1	Iteration Number 20

Here condition in do while is false then also body of loop is executed once.

4 for each loop in java

For each loop is more readable and easier then for loop.

It is used to iterate over array and collection.

Syntax of for each loop in java

for(DataType variable: Elements){
 //body of for each loop
}

for(DataType variable: Elements){

//body of for each loop

}

Difference between for and for each loop is that in for loop we can access index value but not in for each.

Example: Print all array elements using for each loop

public class ForEach {
    public static void main(String[] args) {
        String[] names = {"Ram", "Mohan", "Sohan", "Rohan", "Nita", "Sona"};
        System.out.println("Names are ");
        for (String name : names) {
            System.out.print(name + " ");
        }
    }
}

public class ForEach {

public static void main(String[] args) {

String[] names = {"Ram", "Mohan", "Sohan", "Rohan", "Nita", "Sona"};

System.out.println("Names are ");

for (String name : names) {

System.out.print(name + " ");

}

Output

Names are 
Ram Mohan Sohan Rohan Nita Sona

1 2	Names are Ram Mohan Sohan Rohan Nita Sona

Example: Iterating a student object using for each loop.

Created a class student it contains a method getStudents() to get student list.

Class forEach1 call getStudents() and store its data in studentList.

then for each loop is used to iterate the student object.

import java.util.List;

public class ForEach1 {
    public static void main(String[] args) {
        Student obj = new Student();
        List<Student> studentList = obj.getStudents();
        System.out.println("Student Details are ");
        for (Student student : studentList) {
            System.out.println("RollNo=" + student.getRollNo() + " Name= " + student.getName()
                    + " Class= " + student.getClass1() + " Section= " + student.getSection());
        }
    }
}

import java.util.List;

public class ForEach1 {

public static void main(String[] args) {

Student obj = new Student();

List<Student> studentList = obj.getStudents();

System.out.println("Student Details are ");

for (Student student : studentList) {

System.out.println("RollNo=" + student.getRollNo() + " Name= " + student.getName()

+ " Class= " + student.getClass1() + " Section= " + student.getSection());

}

import java.util.ArrayList;
import java.util.List;

class Student {

    private int rollNo;
    private String name;
    private String class1;
    private String section;
    List<Student> studentList = new ArrayList<Student>();

    public Student() {

    }

    public Student(int rollNo, String name, String class1, String section) {
        this.rollNo = rollNo;
        this.name = name;
        this.class1 = class1;
        this.section = section;
    }

    public List<Student> getStudents() {
        //String[] names = {"Ram", "Mohan", "Sohan", "Rohan", "Nita", "Sona"};
        studentList.add(new Student(1, "Ram", "First Year", "A"));
        studentList.add(new Student(2, "Mohan", "First Year", "A"));
        studentList.add(new Student(3, "Sohan", "Second Year", "A"));
        studentList.add(new Student(4, "Rita", "First Year", "A"));
        studentList.add(new Student(5, "Nita", "Second Year", "A"));
        return studentList;
    }
    public int getRollNo() {
        return rollNo;
    }
    public void setRollNo(int rollNo) {
        this.rollNo = rollNo;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getClass1() {
        return class1;
    }
    public void setClass1(String class1) {
        this.class1 = class1;
    }
    public String getSection() {
        return section;
    }
    public void setSection(String section) {
        this.section = section;
    }
}

import java.util.ArrayList;

import java.util.List;

class Student {

private int rollNo;

private String name;

private String class1;

private String section;

List<Student> studentList = new ArrayList<Student>();

public Student() {

}

public Student(int rollNo, String name, String class1, String section) {

this.rollNo = rollNo;

this.name = name;

this.class1 = class1;

this.section = section;

}

public List<Student> getStudents() {

//String[] names = {"Ram", "Mohan", "Sohan", "Rohan", "Nita", "Sona"};

studentList.add(new Student(1, "Ram", "First Year", "A"));

studentList.add(new Student(2, "Mohan", "First Year", "A"));

studentList.add(new Student(3, "Sohan", "Second Year", "A"));

studentList.add(new Student(4, "Rita", "First Year", "A"));

studentList.add(new Student(5, "Nita", "Second Year", "A"));

return studentList;

}

public int getRollNo() {

return rollNo;

}

public void setRollNo(int rollNo) {

this.rollNo = rollNo;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getClass1() {

return class1;

}

public void setClass1(String class1) {

this.class1 = class1;

}

public String getSection() {

return section;

}

public void setSection(String section) {

this.section = section;

}

Output

Student Details are 
RollNo=1 Name= Ram Class= First Year Section= A
RollNo=2 Name= Mohan Class= First Year Section= A
RollNo=3 Name= Sohan Class= Second Year Section= A
RollNo=4 Name= Rita Class= First Year Section= A
RollNo=5 Name= Nita Class= Second Year Section= A

Student Details are

RollNo=1 Name= Ram Class= First Year Section= A

RollNo=2 Name= Mohan Class= First Year Section= A

RollNo=3 Name= Sohan Class= Second Year Section= A

RollNo=4 Name= Rita Class= First Year Section= A

RollNo=5 Name= Nita Class= Second Year Section= A

5 Examples on Loops

Example: Multiplication table program in java using while loop in Java

import java.util.Scanner;
public class MultiplicationTable {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("Enter a number to generate its table");
        int number = scanner.nextInt();
        int i = 1;
        while (i <= 10) {
            System.out.println(number + " * " + i + " = " + (number * i));
            i++;
        }
    }
}

import java.util.Scanner;

public class MultiplicationTable {

public static void main(String[] args) {

Scanner scanner = new Scanner(System.in);

System.out.println("Enter a number to generate its table");

int number = scanner.nextInt();

int i = 1;

while (i <= 10) {

System.out.println(number + " * " + i + " = " + (number * i));

i++;

}

Output

Enter a number to generate its table
5
5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

Enter a number to generate its table

5 * 1 = 5

5 * 2 = 10

5 * 3 = 15

5 * 4 = 20

5 * 5 = 25

5 * 6 = 30

5 * 7 = 35

5 * 8 = 40

5 * 9 = 45

5 * 10 = 50

Example: Sum of n natural numbers in java using for loop in java

import java.util.Scanner;
public class NaturalNoSum {
    public static void main(String[] args) {
        int sum = 0;
        Scanner scanner = new Scanner(System.in);
        int number = scanner.nextInt();
        for (int i = 1; i <= number; i++) {
            sum += i;
        }
        System.out.println("Sum of first " + number + " natural numbers are " + sum);
    }
}

import java.util.Scanner;

public class NaturalNoSum {

public static void main(String[] args) {

int sum = 0;

Scanner scanner = new Scanner(System.in);

int number = scanner.nextInt();

for (int i = 1; i <= number; i++) {

sum += i;

}

System.out.println("Sum of first " + number + " natural numbers are " + sum);

}

Output

10
Sum of first 10 natural numbers are 55

1 2	10 Sum of first 10 natural numbers are 55

Example Java program to check whether a given number is prime or not

import java.util.Scanner;

public class PrimeNumberChecker {
    public static void main(String[] args) {
        System.out.println("Enter a number to check Prime or Not");
        Scanner scanner = new Scanner(System.in);
        int number = scanner.nextInt();
        int i = 2, count = 0;
        while (i <= number / 2) {
            if (number % i == 0) {
                count++;
                break;
            }
            i++;
        }
        if (count == 0) {
            System.out.println(number + " is prime number");
        } else {
            System.out.println(number + " is not a prime number");
        }
    }
}

import java.util.Scanner;

public class PrimeNumberChecker {

public static void main(String[] args) {

System.out.println("Enter a number to check Prime or Not");

Scanner scanner = new Scanner(System.in);

int number = scanner.nextInt();

int i = 2, count = 0;

while (i <= number / 2) {

if (number % i == 0) {

count++;

break;

}

i++;

}

if (count == 0) {

System.out.println(number + " is prime number");

} else {

System.out.println(number + " is not a prime number");

}

Output

Enter a number to check Prime or Not
23
23 is prime number

Enter a number to check Prime or Not

23 is prime number

Type	Size	Min Max Value
byte	8 bits	-2⁷, 2⁷ -1
short	16 bits	-2¹⁵, 2¹⁵ -1
int	32 bits	-2³¹, 2³¹ -1
long	64 bits	-2⁶³, 2⁶³ -1

Type	Default	Size
float	0.0	32 bits
double	0.0	64 bits

Get String length with String length() method

Finding the length of unicode string in java

Finding the String length in java of unicode characters

Using toCharArray() to find String length in java

Using Function to find the String length in java

Using Recursion to find String length

General form of a class declaration that inherits a super class

Type of Inheritance in Java

Single level Inheritance

Multi level Inheritance

Hierarchical Inheritance

Hybrid Inheritance

Super Class Cant Access Sub Class Member

A sub class can’t access the private member of super class.

String Constructors

Java String Method charAt()

Signature:

Parameters:

Return:

Exception Throws:

Example

Result

Example

Result

Java String Method compareToIgnoreCase()

Signature

Parameters

Return

Example1

Result

Example2

Result

Java String Method indexOf with int parameter

Signature

Parameters

Return

Example

Java String Method indexOf()

Signature

Parameters

Return

Example

Result

Java String Method lastIndexOf

Signature

Parameters

Return

Example

Result

Java String substring() method

Signature

Parameters

Return

Throw

Example

Result

Java String concat() method

Parameters

Example

1 What is StringTokenizer?

2 StringTokenizer Constructors

3 StringTokenizer methods

A Java StringTokenizer countTokens() Method

Signature

Parameters

Return

Example

B Java StringTokenizer hasMoreElements() Method

Parameters

Return

Example

Result

C Java StringTokenizer hasMoreToken() Method

Signature

Parameters

Return

Example

Result

D Java StringTokenizer nextElement() Method

Signature