Java - CharArrayWriter append(CharSequence csq, int start, int end) method

---

---

Description

The Java CharArrayWriter append(CharSequence csq, int start, int end) method appends a portion of the specified character sequence to this writer.

Declaration

Following is the declaration for java.io.CharArrayWriter.append(CharSequence csq, int start, int end) method −

public CharArrayWriter append(CharSequence csq, int start, int end)

Parameters

• csq − The character sequence to be appended. If the character sequence is null, the writer is appended with 4 characters 'null'.

• start − The index of the first character in the portion

• end − The index of the character following the end of the subsequence

Return Value

This CharArrayWriter

Exception

• IndexOutOfBoundsException − If end is greater than sequence's length, start is greater than end, or start or end are negative.

• NullPointerException − If csq is null.

Example - Using CharArrayWriter append(CharSequence csq, int start, int end) method

The following example shows the usage of Java CharArrayWriter append(CharSequence csq, int start, int end) method.

CharArrayWriterDemo.java

package com.tutorialspoint;

import java.io.CharArrayWriter;

public class CharArrayWriterDemo {
   public static void main(String[] args) {      
      CharArrayWriter chw = null;
      
      try {
         // create character array writer
         chw = new CharArrayWriter();
         
         // declare character sequence
         CharSequence csq = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
         
         // append character sequence to the writer
         chw.append(csq, 2, 5);
         
         // prints out the character sequences
         System.out.println(chw.toString());
         
      } catch(Exception e) {
         // for any error
         e.printStackTrace();
      } finally {
         // releases all system resources from writer
         if(chw!=null)
            chw.close();
      }
   }
}

Output

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

CDE

Example - Appending a Substring from a String

The following example shows the usage of Java CharArrayWriter append(CharSequence csq, int start, int end) method.

CharArrayWriterDemo.java

package com.tutorialspoint;

import java.io.CharArrayWriter;

public class CharArrayWriterDemo {
   public static void main(String[] args) {
      CharArrayWriter writer = new CharArrayWriter();

      // Define a CharSequence (String)
      String text = "Hello, Java World!";

      // Append a substring from index 7 to 11 ("Java")
      writer.append(text, 7, 11);

      // Print the output
      System.out.println(writer.toString()); // Output: Java
   }
}

Output

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

Java

Explanation

• A CharArrayWriter instance is created.

• A String "Hello, Java World!" is defined.

• The append(CharSequence csq, int start, int end) method appends characters from index 7 to 11 (substring "Java").

• The result ("Java") is printed.

Example - Appending a Subsequence from a StringBuilder

The following example shows the usage of Java CharArrayWriter append(CharSequence csq, int start, int end) method.

CharArrayWriterDemo.java

package com.tutorialspoint;

import java.io.CharArrayWriter;

public class CharArrayWriterDemo {
   public static void main(String[] args) {
      CharArrayWriter writer = new CharArrayWriter();

      // Create a StringBuilder
      StringBuilder sb = new StringBuilder("Spring Boot Framework");

      // Append a substring from index 7 to 11 ("Boot")
      writer.append(sb, 7, 11);

      // Append another substring from index 12 to 21 ("Framework")
      writer.append(sb, 12, 21);

      // Print the output
      System.out.println(writer.toString()); // Output: BootFramework
   }
}

Output

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

BootFramework

Explanation

• A StringBuilder "Spring Boot Framework" is created.

• The append method extracts "Boot" (index 7 to 11) and appends it.

• Another call extracts "Framework" (index 12 to 21) and appends it.

• The final output is "BootFramework".

Key Takeaways

• Allows appending a specific range of characters from a CharSequence.

• Supports String, StringBuilder, and StringBuffer.

• Helps extract parts of text efficiently without extra substring operations.