Replace in Java: Everything you Need to Know

Replacing a number or string of characters is an interesting thing to do, be it Java, Python or any other programming language. In this article, however, we will focus on Replace in Java in the following order:

• Types of Replace
• Replace
• ReplaceAll
• ReplaceFirst

Types of Replace in Java

There are three methods of replacing Java String.

• Replace
• ReplaceAll
• ReplaceFirst

With the help of these options, you can replace any character in a string.

Replace in Java

String replace(): This method returns a new string as output by replacing every occurrence of the character with a new Character.

Syntax:

public Str replace(char oldC, char newCh)

Parameters:

oldCh − old character

newCh − new character

Return Value:

This replaces oldCh with newCh in the string.

Code:

public class Ex1 {
    public static void main(String args[]) {
        String S1 = new String("the quick fox jumped");
        System.out.println("Original String is ': " + S1);
        System.out.println("String after replacing 'cat' with 'dog': " + S1.replace("cat", "dog"));
        System.out.println("String after replacing all 't' with 'a': " + S1.replace('t', 'a'));

    }
}

Output:

Original String is ': the cat jumped
String after replacing ‘cat' with 'dog': the dog jumped
String after replacing all’t’ with 'a': ahe quick fox jumped

ReplaceAll

Java String Replaceall(): This method returns a new string replacing all the sequence of characters matching a regular expression and the replacement string.

Syntax:

public Str replaceAll(String regex, String replacement)

Parameters:

regx: regular expression
replacement: replacement sequence of characters

Code:

public class Ex2 {
    public static void main(String args[]) {
        String str = "Java web replace method";
        //remove white spaces
        String str2 = str.replaceAll("s", "");
        System.out.println(str2);
    }
}

Output:

Javewebreplacemethod

ReplaceFirst

Java String replaceFirst(): This method replaces the first substring of any given string which matches that regular expression.

Syntax:

public Str replaceFirst(String rgex, String replacement)

Parameters:

rgex − the regular expression to which given string needs to matched. 

replacement − the string that replaces regular expression.

Code:

public class Ex3 {
    public static void main(String args[]) {
        String str = "This is an example of replace";
        //Only Replace first 'i' with '7' 
        String str1 = str.replaceFirst("i", "7");
        System.out.println(str1);
    }
}

Output:

Th7s is an example of replace.

With this, we come to the end of this article. I hope you got an understanding of how to replace strings and characters.

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