Java Program to Replace Multiple Characters in a String

06 Jun, 2021
In this program, we will be discussing various methods for replacing multiple characters in String. This can be done using the methods listed below: 
Using String.replace() method
Using replaceAll() method 
Using replaceFirst() method 
Method 1: Using String.replace() method
This method returns a new string resulting from replacing all occurrences of old characters in the string with new characters.
Syntax:
public String replace(char oldch, char newch)
Parameters:
The old character.
The new character.
Return Value: It returns a string derived from this string by replacing every occurrence of old character with a new character.
Example 
Java
// Java code to demonstrate the// working of replace()public class rep1 {public static void main(String args[]) {              // Initialising String    String Str = new String("Welcome to geeksforgeeks");              // Using replace to replace characters    System.out.print("After replacing all o with T : " );    System.out.println(Str.replace('o', 'T'));              // Using replace to replace characters    System.out.print("After replacing all e with D : " );    System.out.println(Str.replace('e', 'D'));          }}
After replacing all o with T : WelcTme tT geeksfTrgeeks
After replacing all e with D : WDlcomD to gDDksforgDDks
Method 2: Using replaceAll() method 
This method replaces each substring of the string that matches the given regular expression with the given replace_str.
Syntax:
public String replaceAll(String regex, String replace_str)
Parameters:
regex: the regular expression to which this string is to be matched.
replace_str: the string which would replace found expression.
Return Value: This method returns the resulting String.
Example 
Java
// Java code to demonstrate the// working of replaceAll()public class rep2 {public static void main(String args[]) {              // Initialising String    String Str = new String("Welcome to geeksforgeeks");              // original string    System.out.print("Original String : " );    System.out.println(Str);              // Using replaceAll to replace regex with replace_str    System.out.print("After replacing regex with replace_str : " );    System.out.println(Str.replaceAll("(.*)geeks(.*)", "AKSHIT SAXENA"));          }}
Original String : Welcome to geeksforgeeks
After replacing regex with replace_str : AKSHIT SAXENA
Method 3: Using replaceFirst() method 
This method replaces the first substring of this string that matches the given regular expression with the given replace_str.
Syntax:
public String replaceFirst(String regex, String replace_str)
Parameters
regex: The regular expression to which this string is to be matched.
replace_str: The string which would replace found expression.
Return value: This method returns a resulting string.
Example
Java
// Java code to demonstrate the// working of replaceFirst()public class rep3 {public static void main(String args[]) {              // Initialising String    String Str = new String("Welcome to geeksforgeeks");              // original string    System.out.print("Original String : " );    System.out.println(Str);              // Using replaceFirst to replace regex with replace_str    // Replaces 1st occurrence of geeks with ASTHA    System.out.print("After replacing 1st occurrence of regex with replace_str : " );    System.out.println(Str.replaceFirst("geeks", "Akshit"));          }}
Original String : Welcome to geeksforgeeks
After replacing 1st occurrence of regex with replace_str : Welcome to Akshitforgeeks
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