StringBuffer replace() Method in Java with Examples

Difficulty Level : Basic
Last Updated : 14 Oct, 2019

The StringBuffer.replace() is the inbuilt method which is used to replace the characters in a substring of this sequence with the characters in the specified String. Here simply the characters in the substring are removed and other char is inserted at the start.

Syntax :

public StringBuffer replace(int first, int last, String st)

Parameters : The method accepts three parameters.

first : This is of integer type which refers to the starting index.
last : This is of integer type which refers to the ending index.
st : This is of string type which refer to the String that will replace previous contents.

Return Value : The method returns this object after performing the above mentioned operations.

Exception : If the first is negative, greater than length(), or greater than last then StringIndexOutOfBoundsException.

Examples :

Input:
StringBuffer= "The first planet of solar system is merrhxy"
first = 39
last = 42
st = "cur"

Output: The first planet of solar system is mercury

Below programs illustrate the java.lang.StringBuffer.replace() method:
Program 1:

// Java praogram to illustrate the 
// java.lang.StringBuffer.replace() 
  
import java.lang.*; 
  
public class Geeks { 
  
    public static void main(String[] args) 
    { 
  
        StringBuffer sbf = new StringBuffer("Welcome to Geekshssgeeks"); 
        System.out.println("string buffer = " + sbf); 
  
        // Replacing substring from index 15 to index 18 
        sbf.replace(15, 18, "for"); 
  
        System.out.println("After replacing string buffer= " + sbf); 
    } 
} 

Output:

string buffer = Welcome to Geekshssgeeks
After replacing string buffer= Welcome to Geekforsgeeks

Program 2: When negative index is passed:

// Java praogram to illustrate the 
// java.lang.StringBuffer.replace() 
  
import java.lang.*; 
  
public class Geeks { 
  
    public static void main(String[] args) 
    { 
  
        StringBuffer sbf = new StringBuffer("Welcome to Geekshssgeeks"); 
        System.out.println("string buffer = " + sbf); 
  
        // Replacing substring from index -15 to index -18 
        sbf.replace(-15, -18, "for"); 
  
        System.out.println("After replacing string buffer= " + sbf); 
    } 
} 

Output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: 
String index out of range: -15
at java.lang.AbstractStringBuilder.replace(AbstractStringBuilder.java:851)
at java.lang.StringBuffer.replace(StringBuffer.java:452)
at Geeks.main(Geeks.java:14)

Program 3: When index passed is greater than length

// Java praogram to illustrate the 
// java.lang.StringBuffer.replace() 
  
import java.lang.*; 
  
public class Geeks { 
  
    public static void main(String[] args) 
    { 
  
        StringBuffer sbf = new StringBuffer("Welcome to Geekshssgeeks"); 
        System.out.println("string buffer = " + sbf); 
  
        // Replacing substring from index 215 to index 218 
        sbf.replace(215, 218, "for"); 
  
        System.out.println("After replacing string buffer= " + sbf); 
    } 
} 

Output:

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: 
start > length()
at java.lang.AbstractStringBuilder.replace(AbstractStringBuilder.java:853)
at java.lang.StringBuffer.replace(StringBuffer.java:452)
at Geeks.main(Geeks.java:14)

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