Java.lang.string.replace() method in Java

Here are three variants of replace() method.This article depicts about all of them ,as follows:
1. String replace() : 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:
oldch : the old character.
newch : the new character.
Return Value
It returns a string derived from this string by replacing every occurrence of oldch with newch.
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// 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'));
        
   }
}

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Output:

After replacing all o with T : WelcTme tT geeksfTrgeeks
After replacing all e with D : WDlcomD to gDDksforgDDks

2. String replaceAll() :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.
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// 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(.*)", "ASTHA TYAGI"));
        
   }
}

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Output:

Original String : Welcome to geeksforgeeks
After replacing regex with replace_str : ASTHA TYAGI

3. String replaceFirst() :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.
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// 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", "ASTHA"));
        
   }
}

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Output:

Original String : Welcome to geeksforgeeks
After replacing 1st occurrence of regex with replace_str  : Welcome to ASTHAforgeeks

This article is contributed by Astha Tyagi. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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