Java String Tutorial | String replace methods example

String replace methods are used to replace a part of string with a new string.
We have 4 variations for replace in String

String replace(char oldChar, char newChar)
String replace(CharSequence target, CharSequence replacement)
String replaceAll(String regex, String replacement)
String replaceFirst(String regex, String replacement)

String replace(char oldChar, char newChar)

String replace(CharSequence target, CharSequence replacement)

String replaceAll(String regex, String replacement)

String replaceFirst(String regex, String replacement)

String replace(char oldChar, char newChar) returns a new String with the oldChar replaced with a newChar that was specified.

String replace(CharSequence target, CharSequence replacement) returns a new String by replacing a sequence of characters that are specified.

String replaceAll(String regex, String replacement) returns a new String by replacing all the matching regular expression with a new replacement String.

String replaceFirst(String regex, String replacement) returns a new String by replacing only the first matching regular expression with a new replacement String.

String replace methods example

1. replace() example

package com.kscodes.sampleproject;

public class StringReplaceExample {
	public static void main(String[] args) {

		String testStr1 = "We have so many characters to replace";

		System.out.println("Using replace(char,char) to replace all 'a' with '$'");
		System.out.println("Original String ::" + testStr1);
		System.out.println("Replaced String ::" + testStr1.replace('a', '$'));

		System.out.println("----------------------------------------------------");
		
		String testStr2 = "I will learn java. I will code in java";
		CharSequence cs1 = "will";
		CharSequence cs2 = "did";
		

		System.out.println("Using replace(CharSequence ,CharSequence ) to replace all 'will' with 'did'");
		System.out.println("Original String ::" + testStr2);
		System.out.println("Replaced String ::" + testStr2.replace(cs1,cs2));

	}

}

package com.kscodes.sampleproject;

public class StringReplaceExample {

public static void main(String[] args) {

String testStr1 = "We have so many characters to replace";

System.out.println("Using replace(char,char) to replace all 'a' with '$'");

System.out.println("Original String ::" + testStr1);

System.out.println("Replaced String ::" + testStr1.replace('a', '$'));

System.out.println("----------------------------------------------------");

String testStr2 = "I will learn java. I will code in java";

CharSequence cs1 = "will";

CharSequence cs2 = "did";

System.out.println("Using replace(CharSequence ,CharSequence ) to replace all 'will' with 'did'");

System.out.println("Original String ::" + testStr2);

System.out.println("Replaced String ::" + testStr2.replace(cs1,cs2));

}

Output

Using replace(char,char) to replace all 'a' with '$'
Original String ::We have so many characters to replace
Replaced String ::We h$ve so m$ny ch$r$cters to repl$ce
----------------------------------------------------
Using replace(CharSequence ,CharSequence ) to replace all 'will' with 'did'
Original String ::I will learn java. I will code in java
Replaced String ::I did learn java. I did code in java

Using replace(char,char) to replace all 'a' with '$'

Original String ::We have so many characters to replace

Replaced String ::We h$ve so m$ny ch$r$cters to repl$ce

----------------------------------------------------

Using replace(CharSequence ,CharSequence ) to replace all 'will' with 'did'

Original String ::I will learn java. I will code in java

Replaced String ::I did learn java. I did code in java

2. replaceAll() example

package com.kscodes.sampleproject;

public class StringReplaceAllExample {

	public static void main(String[] args) {
		
		String testStr1 = "We will replace 12345. Also we will replace 111 and also 345";
		
		System.out.println("Using replaceAll to replace all numbers with '@@'");
		System.out.println("Original String ::" + testStr1);
		System.out.println("Replaced String ::" + testStr1.replaceAll("[0-9]+", "@@"));
		
		System.out.println("------------------------------------------------");
		
		String testStr2 = "This is to test replaceAll for String";
		
		System.out.println("Using replaceAll to replace all occureneces of 'is' with 00");
		System.out.println("Original String ::" + testStr2);
		System.out.println("Replaced String ::" + testStr2.replaceAll("is", "00"));
	}

}

package com.kscodes.sampleproject;

public class StringReplaceAllExample {

public static void main(String[] args) {

String testStr1 = "We will replace 12345. Also we will replace 111 and also 345";

System.out.println("Using replaceAll to replace all numbers with '@@'");

System.out.println("Original String ::" + testStr1);

System.out.println("Replaced String ::" + testStr1.replaceAll("[0-9]+", "@@"));

System.out.println("------------------------------------------------");

String testStr2 = "This is to test replaceAll for String";

System.out.println("Using replaceAll to replace all occureneces of 'is' with 00");

System.out.println("Original String ::" + testStr2);

System.out.println("Replaced String ::" + testStr2.replaceAll("is", "00"));

}

Output

Using replaceAll to replace all numbers with '@@'
Original String ::We will replace 12345. Also we will replace 111 and also 345
Replaced String ::We will replace @@. Also we will replace @@ and also @@
------------------------------------------------
Using replaceAll to replace all occureneces of 'is' with 00
Original String ::This is to test replaceAll for String
Replaced String ::Th00 00 to test replaceAll for String

Using replaceAll to replace all numbers with '@@'

Original String ::We will replace 12345. Also we will replace 111 and also 345

Replaced String ::We will replace @@. Also we will replace @@ and also @@

------------------------------------------------

Using replaceAll to replace all occureneces of 'is' with 00

Original String ::This is to test replaceAll for String

Replaced String ::Th00 00 to test replaceAll for String

3. replaceFirst() example

package com.kscodes.sampleproject;

public class StringReplaceFirstExample {

	public static void main(String[] args) {

		String testStr1 = "We will replace 12345. Also we will replace 111 and also 345";

		System.out.println("Using replaceFirst to replace all numbers with '@@'");
		System.out.println("Original String ::" + testStr1);
		System.out.println("Replaced String ::"	+ testStr1.replaceFirst("[0-9]+", "@@"));
		
		System.out.println("------------------------------------------------");
		
		String testStr2 = "This is to test replaceAll for String";
		
		System.out.println("Using replaceFirst to replace first occurenece of 'is' with 00");
		System.out.println("Original String ::" + testStr2);
		System.out.println("Replaced String ::" + testStr2.replaceFirst("is", "00"));

	}

}

package com.kscodes.sampleproject;

public class StringReplaceFirstExample {

public static void main(String[] args) {

String testStr1 = "We will replace 12345. Also we will replace 111 and also 345";

System.out.println("Using replaceFirst to replace all numbers with '@@'");

System.out.println("Original String ::" + testStr1);

System.out.println("Replaced String ::" + testStr1.replaceFirst("[0-9]+", "@@"));

System.out.println("------------------------------------------------");

String testStr2 = "This is to test replaceAll for String";

System.out.println("Using replaceFirst to replace first occurenece of 'is' with 00");

System.out.println("Original String ::" + testStr2);

System.out.println("Replaced String ::" + testStr2.replaceFirst("is", "00"));

}

Output

Using replaceFirst to replace all numbers with '@@'
Original String ::We will replace 12345. Also we will replace 111 and also 345
Replaced String ::We will replace @@. Also we will replace 111 and also 345
------------------------------------------------
Using replaceFirst to replace first occurenece of 'is' with 00
Original String ::This is to test replaceAll for String
Replaced String ::Th00 is to test replaceAll for String

Using replaceFirst to replace all numbers with '@@'

Original String ::We will replace 12345. Also we will replace 111 and also 345

Replaced String ::We will replace @@. Also we will replace 111 and also 345

------------------------------------------------

Using replaceFirst to replace first occurenece of 'is' with 00

Original String ::This is to test replaceAll for String

Replaced String ::Th00 is to test replaceAll for String

Reference

1. String API