Java StringBuffer replace()

In this tutorial, we will discuss Java StringBuffer replace() method with the help of examples.

Syntax of replace() method:

//replace substring from index 4 to 9 by given string "hello"
//4 is inclusive and 9 is exclusive
sb.replace(4, 9, "hello");

replace() Description

public StringBuffer replace(int start, int end, String str): Replace the substring starting from start index till end index with the given string str.

replace() Parameters

The replace() method of Java StringBuffer class takes three parameters:

• start: Represents the start of substring that is going to be replaced.
• end: Represents the end of the substring that is going to be replaced.
• str: This string is going to replace the substring marked by start and end index.

replace Return Value

• Returns a StringBuffer object that contains the new string after replacement.

This method throws StringIndexOutOfBounds Exception, if any of the following condition occurs:

• start index < 0
• start index > length of the string

Example 1: Replace a given string with another string

public class JavaExample {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("Hello Guys");
    System.out.println("Given Sequence : "+sb);

    //replace the substring
    sb.replace(6, 10, "World");
    System.out.println("New Sequence: "+sb);
  }
} 

Output:

Example 2: If replace string is smaller than the given string

public class JavaExample {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("AnotherText");
    System.out.println("Given Sequence: "+sb);

    sb.replace(0, sb.length(), "Text");
    System.out.println("New Sequence: "+sb);
  }
} 

Output:

Example 3: If endIndex is greater than the length of given string

public class JavaExample {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("Hello");
    System.out.println("Given Sequence: "+sb);
    //end index is greater than original string length
    sb.replace(0, 100, "Hi");
    System.out.println("New Sequence: "+sb);
  }
} 

Output:

Example 4: If startIndex is Negative

public class JavaExample {
  public static void main(String[] args) {
    StringBuffer sb = new StringBuffer("Text");
    //start index is negative
    sb.replace(-5, 10, "AnotherText");
    System.out.println("String after replace: "+sb);
  }
} 

Output:

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