Java - Writer class

---

---

Introduction

The Java Writer class is a abstract class for writing to character streams.

Class declaration

Following is the declaration for Java.io.Writer class −

public abstract class Writer
   extends Object
      implements Appendable, Closeable, Flushable

Field

Following are the fields for Java.io.Writer class −

• protected Object lock − This is the object used to synchronize operations on this stream.

Class constructors

Class methods

Methods inherited

This class inherits methods from the following classes −

• Java.io.Object

Example - Using StringWriter to Append Characters

The following example shows the usage of Writer append(char c) method.

WriterDemo.java

package com.tutorialspoint;

import java.io.StringWriter;

public class WriterDemo {
   public static void main(String[] args) {
      StringWriter writer = new StringWriter();
      writer.append('H');
      writer.append('i');
      writer.append('!');

      System.out.println("Output: " + writer.toString());
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Output: Hi!

Explanation

• Each append(char) call adds a single character.

• "H" + "i" + "!" = "Hi!" is stored in the writer.

Example - Using FileWriter with close()

The following example shows the usage of Writer close() method.

WriterDemo.java

package com.tutorialspoint;

import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class WriterDemo {
   public static void main(String[] args) {
      try {
         Writer writer = new FileWriter("example1.txt");
         writer.write("Hello, this is a test.");
         writer.close(); // Closing the writer to release resources
         System.out.println("File written and writer closed.");
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result−

File written and writer closed.

Explanation

• A FileWriter writes text to a file.

• After writing, writer.close() is called to−

  • Flush the stream (if needed),

  • Release file locks and system resources,

  • Prevent memory leaks.

• Writing again after close() will throw an exception.

Example - Using BufferedWriter with flush()

The following example shows the usage of Writer flush() method.

WriterDemo.java

package com.tutorialspoint;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class WriterDemo {
   public static void main(String[] args) {
      try {
         Writer writer = new BufferedWriter(new FileWriter("flush1.txt"));
         writer.write("First part of the content.");
         writer.flush();  // Forces the buffer to write to file
         System.out.println("Buffer flushed after first write.");

         writer.write(" Second part added.");
         writer.flush();  // Flush again before closing
         System.out.println("Buffer flushed after second write.");

         writer.close();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

Let us compile and run the above program, this will produce the following result−

Buffer flushed after first write.
Buffer flushed after second write.

Explanation

• BufferedWriter uses an internal buffer.

• flush() ensures the content is written immediately to the file, even if the buffer isn't full.

• Useful when you want to make sure data is written without closing the stream.