In this example we will show how to modify a string by replacing either characters or sequences of characters included in the string with different ones.

1. String Replace methods in Java

TheString provides 4 methods for replacing strings.

• String replace(char oldChar, char newChar)
  This method replaces every occurrence of the oldChar in the string with the newChar and returns the updated string.
• String replace(CharSequence target, CharSequence replacement)
  This method replaces every occurrence of the target sequence of characters in the string with the replacement sequence of characters.
• String replaceAll(String regularExpr, String replacement)
  This method replaces every substring in the given string that matches the regular expression, with the replacemet substring.
• String replaceFirst(String regularExpr, String replacement)
  This method replaces the first occurrence of the substring that matches the regular expression, with the replacement string.

2. String replace example

Create a java class namedReplaceExample.java with the following code:

ReplaceExample.java

package com.javacodegeeks.javabasics.replace;public class ReplaceExample {public static void main(String[] args) {String oldstr = "java.code.geeks";System.out.println("Original string is: " + oldstr);// this method replaces every occurrence of the character . with the// character _String newstr1 = oldstr.replace('.', '_');System.out.println("New string1 is: " + newstr1);// this method replaces every occurrence of the character sequence// "code" with the// character sequence "jcg"String newstr2 = oldstr.replace("code", "jcg");System.out.println("New string2 is: " + newstr2);String regex = "[a,e]";// this method replaces every occurrence of the characters in the// regular expression// with the character *String newstr3 = oldstr.replaceAll(regex, "*");System.out.println("New string3 is: " + newstr3);// this method replaces the first occurrence of any of the characters in// the regular expression// with the character *String newstr4 = oldstr.replaceFirst(regex, "*");System.out.println("New string4 is: " + newstr4);}}

If we run the above code, we will have the following results:

• Output:

Original string is: java.code.geeksNew string1 is: java_code_geeksNew string2 is: java.jcg.geeksNew string3 is: j*v*.cod*.g**ksNew string4 is: j*va.code.geeks

3. Download the source code

This was an example of string replace in Java. You can download the source code from here:StringReplaceExample.zip

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