Java – String replace(), replaceFirst() and replaceAll() method

In this tutorial we will discuss replace(), replaceFirst()and replaceAll() methods. All of these methods are mainly used for replacing a part of String with another String.
String replace(char oldChar, char newChar): It replaces all the oldChar characters with newChar characters. For e.g. "pog pance".replace('p', 'd') would return dog dance.
String replaceFirst(String regex, String replacement): It replaces the first substring that fits the specified regular expression with the replacement String. PatternSyntaxException if the specified regular expression(regex) is not valid.
String replaceAll(String regex, String replacement): It replaces all the substrings that fits the given regular expression with the replacement String.

Example 1:replace() Method

public class Example1{
   public static void main(String args[]){
       String str = new String("Site is BeginnersBook.com");

       System.out.print("String after replacing all 'o' with 'p' :" );
       System.out.println(str.replace('o', 'p'));

       System.out.print("String after replacing all 'i' with 'K' :" );
       System.out.println(str.replace('i', 'K'));
   }
}

Output:

String after replacing all 'o' with 'p' :Site is BeginnersBppk.cpm
String after replacing all 'i' with 'K' :SKte Ks BegKnnersBook.com

Example 2:replaceFirst() Method

public class Example2{
   public static void main(String args[]){
       String str = new String("Site is BeginnersBook.com");

       System.out.print("String after replacing com with net :" );
       System.out.println(str.replaceFirst("com", "net"));

       System.out.print("String after replacing Site name:" );
       System.out.println(str.replaceFirst("Beginners(.*)", "XYZ.com"));
   }
}

Output:

String after replacing com with net :Site is BeginnersBook.net
String after replacing Site name:Site is XYZ.com

Example 3:replaceAll() Method

public class Example3{
   public static void main(String args[]){
       String str = new String("My .com site is BeginnersBook.com");
       System.out.print("String after replacing all com with net :" );
       System.out.println(str.replaceAll("com", "net"));
   }
}

Output:

String after replacing all com with net :My .net site is BeginnersBook.net