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Concatenate & Buffer File in Java
Concatenate: It is possible to concatenate two or more files and save in a different file.
In java, by using SequenceInputStream class we can concatenate two or more files.
Buffer Files: In java, we can create a buffer to store temporary data that is read from & written to a stream and this process known as i/o buffer operation.
Buffer is sit between programmer and source/destination file.
Buffer can be created by using following classes:
- BufferedInputClass
- BufferedOutputClass
Example: write a program to concatenate two file A & B and concatenated data print on output screen.
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import java.io.*; public class FileConcat { public static void main(String arg[]) throws IOException { FileInputStream I1 = null; FileInputStream I2 = null; I1 = new FileInputStream("A.txt"); //open file A for concatenate I2 = new FileInputStream("B.txt"); //open file B for concatenate // declare sis to store combined file SequenceInputStream sis = null; sis = new SequenceInputStream(I1, I2); // create buffer for input output BufferedInputStream ibs = new BufferedInputStream(sis); BufferedOutputStream obs = new BufferedOutputStream(System.out); int c; while ((c = ibs.read()) != -1) // read& write till the end of buffer { obs.write((char) c); } ibs.close(); obs.close(); I1.close(); I2.close(); } } |
Suppose we have a File “A.txt”
| Hello students I am aditya. |
and File “B.txt”
| Hello |
Output: Hello students I am
Example: Write a program to copy the content of one file to another file using buffer/BufferReader.
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import java.io.*; public class FileCopy1 { public static void main(String[] args) throws IOException { PrintWriter pw = new PrintWriter("B.txt"); // PrintWriter for write on file B BufferedReader br = new BufferedReader(new FileReader("A.txt")); String line = br.readLine(); // read first line from file A while (line != null) // loop to copy each line of A.txt to C.txt { pw.println(line); line = br.readLine(); } pw.flush(); // closing resources br.close(); pw.close(); } } |
Suppose we have a File “A .txt”
| Hello students I am aditya. |
Output: File “B”
| Hello students I am aditya. |
Note: If there is no file “B” it will be create automatically.
Example: Write a program to concatenate two
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import java.io.*; public class FileMerge { public static void main(String[] args) throws IOException { PrintWriter pw = new PrintWriter("C.txt"); // PrintWriter for write on C.txt // BufferedReader object for A.txt BufferedReader br = new BufferedReader(new FileReader("A.txt")); String line = br.readLine(); // read first line from file A while (line != null) // loop to copy each line of A.txt to C.txt { pw.println(line); line = br.readLine(); } br = new BufferedReader(new FileReader("B.txt")); line = br.readLine(); // read first line from file B while (line != null) // loop to copy each line of B.txt to C.txt { pw.println(line); line = br.readLine(); } pw.flush(); // closing resources br.close(); pw.close(); } } |
Suppose we have a File “A.txt” and File “B.txt”
| Hello students I am aditya. |
| Hello |
Output: File “C”
| Hello students I am aditya. Hello |
Note: Ifthere is no file “C” it will be create automatically.
File I/O with Primitive Data Type In Java
In java, basic input-output stream provides a method for reading & writing bytes or character in a file. If we want to read-write primitive data typa(such as int , float etc.) than we can use filter classes to filter data in the original stream.
DataInputStream & DataOutputStream are two filter classes used for creating “data streams” for handling primitive data type.
Example: Write a program to write & read a primitive data on a same file.
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import java.io.*; public class PrimitiveReadWrite { public static void main(String args[]) throws IOException { FileOutputStream o = new FileOutputStream("A.txt"); //Open file “A” for write DataOutputStream O = new DataOutputStream(o); //write primitive data on file A O.writeInt(1999); O.writeDouble(333.89); O.writeBoolean(false); O.writeChar('X'); O.close(); o.close(); //read primitive data from file A FileInputStream i = new FileInputStream("A.txt"); //open file A for read DataInputStream I = new DataInputStream(i); System.out.println(I.readInt()); System.out.println(I.readDouble()); System.out.println(I.readBoolean()); System.out.println(I.readChar()); I.close(); i.close(); } } |
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Output: 1999 333.89 false X |
Character Stream I/O in Java
In a java programming, like a Byte stream Character stream is also used for input-output for 16 bit. But Byte streams are used to perform input and output of 8-bit.
Most common Character streams classes are, FileReader and FileWriter.
FileReader- FileReader uses for reads two bytes at a time.
FileWriter– FileWriter uses for writes two bytes at a time.
Example: Write a program, to copy the content of file A into file B using Byte stream class.
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import java.io.*; public class FileReaderExample { public static void main(String arg[]) throws IOException { FileReader I = null; FileWriter O = null; try { I = new FileReader("A.txt"); O = new FileWriter("B.txt"); int c; while ((c = I.read()) != -1) { O.write(c); } } finally { if (I != null) { I.close(); } if (O != null) { O.close(); } } } } |
Note: if there is only file A in which data is written and no file B then, file B will be create automatically.
Suppose we have a File “A”
| Hello students I am aditya. |
Output: When we run above program one new file create with Name “B” and content of file “A” will be copy into file “B”.
File “B”
| Hello students I am aditya. |
Byte Streams in Java
In java programming, to perform input and output of 8-bit, Byte stream is used.
Most common byte streams classes are, FileInputStream and FileOutputStream.
FileInputStream : FileInputStream is used for reads one byte at a time .
FileOutputStream : FileOutputStream is used for writes one byte at a time
Writing Bytes
Example: Write a program, to write a bytes to a file using Byte stream class.
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import java.io.*; public class WriteBytes { public static void main(String args[]) throws IOException { byte b[] = { 'h', 'e', 'l', 'l', 'o', 'a', 'd', 'i' }; //create a byte array FileOutputStream out = null; try { out = new FileOutputStream("A.txt"); //open file A for write out.write(b); // write byte data to file output } finally { out.close(); } } } |
Result
checking file A.txt it will show following content.
Note: If there is no file A then, file A will be create automatically
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helloadi |
Reading bytes from a file
Suppose we have a file “A.txt”
| Hello Students I am Aditya |
Example: Write a program, to read a bytes from file A using Byte stream class and print on output screen.
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import java.io.*; public class ReadBytes { public static void main(String args[]) throws IOException { FileInputStream in = null; try { in = new FileInputStream("A.txt"); int c; while ((c = in .read()) != -1) { System.out.print((char) c); } } finally { in .close(); } } } |
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Hello Students I am Aditya |
Example: Write a program, to copy the content of file A into file B using Byte stream class.
Note: if there is only file A in which data is written and no file B then, file B will be create automatically.
Suppose we have a File “A”
| Hello students I am aditya. |
Output: When we run above program one new file create with Name “B” and content of file “A” will be copy into file “B”.
File “B”
| Hello students I am aditya. |
File and Input Output in Java
In Java programming, to perform the input-output in file handling Java has a java.io package which contain contains nearly every class you might ever need.
In file
Stream
In java programming, a sequence of data defined as a “stream”.
Simply there are two type of streams:
- InputStream − To read data from a source InputStream is used.
- OutputStream- To write a data to a destination OutputStream is used.
Stream Classes
In java, package “java.io” contains a large number of stream classes and these classes can be divided into two groups:
- Byte stream
- Character stream
Thread Life Cycle in Java
Life cycle of Thread tells the various information of thread form born to terminate. Thread life cycle contains the several stages and at a time any thread can be present in a single state.
States of Thread life cycle
- Born
- Ready
- Running
- Blocked
- Sleep
- Wait
- Dead
Ready: In this state thread is ready to execute but not running.
When the start() method calls thread enters from born to ready state.
Running: When a run() method executes highest priority ready thread assigned a processor and enter in a running state for execution.
Thread can visit more than ones in a running state.
Blocked: When a running thread has a input-output issue it enters in a blocked state from running state and when input-output issue solves it again comes in a running thread.
When sleep time expires then thread moves to ready state.
When a high priority thread execution completes it calls
Dead: A running thread is enter in a dead state when its execution completes (run() method completes) or terminate for any reason.
Thread isAlive() and join() Methods in Java
There are two ways to determine whether a thread has finished or not.
- isAlive()
- join()
isAlive(): isAlive() method is used to check whether a thread is in the running or not .
or
In a another word, this method determines thread is live or dead.
isAlive( )method returns true if the thread is still running otherwise it returns false.
join(): This method wait for the specified thread to terminate.
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import java.lang.*; public class Demo implements Runnable { public void run() { Thread t = Thread.currentThread(); // tests if this thread is alive System.out.println("thread is live = " + t.isAlive()); // tests if this thread is alive } public static void main(String args[]) throws Exception { Thread t = new Thread(new Demo()); t.start(); // this will call run() function t.join(); // waits for this thread to die System.out.println("thread is live = " + t.isAlive()); // tests if this thread is alive } } |
Result
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thread is live = true thread is live = false |
Thread suspend() and resume() method in Java
suspend() : This method
resume() : This method revives the suspended thread.
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class A extends Thread { public void run() { for (int i = 1; i <= 5; i++) { System.out.println("A" + i); } System.out.println("Exit from A"); } } class B extends Thread { public void run() { for (int i = 1; i <= 5; i++) { System.out.println("B" + i); } System.out.println("Exit from B"); } } public class TestMain { public static void main(String args[]) { A a = new A(); B b = new B(); a.start(); b.start(); a.suspend(); a.resume(); } } |
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A1 A2 A3 A4 A5 Exit from A B1 B2 B3 B4 B5 Exit from B |
Thread stop method in Java
In java, stop() method kills/terminates the currently executing thread.
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class A extends Thread { public void run() { for (int i = 1; i <= 5; i++) { if (i == 3) stop(); System.out.println("A" + i); } System.out.println("Exit from A"); } } public class TestMain { public static void main(String args[]) { A a = new A(); a.start(); } } |
Result
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A1 A2 |
Description: in the above program, when
Thread Yield method in Java
In
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class A extends Thread { public void run() { for (int i = 1; i <= 5; i++) { if (i == 2) yield(); System.out.println("A" + i); } System.out.println("Exit from A"); } } class B extends Thread { public void run() { for (int i = 1; i <= 5; i++) { System.out.println("B" + i); } System.out.println("Exit from B"); } } public class xyz { public static void main(String args[]) { A a = new A(); B b = new B(); a.start(); b.start(); } } |
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A1 A2 A3 A4 A5 Exit from A B1 B2 B3 B4 B5 Exit from B |