Difference Between replace() and replaceAll() in Java

The Java String class provides various methods to manipulate string. The replace() and replaceAll() method are one of them that are used to replace a string with a specified sub string. As the name of both the methods sounds same but their working is different.

Let's understand replace(), replaceAll() and replaceFirst() methods and differentiate each one of them one by one.

String.replace() Method

The replace() method is one of the most used string methods for replacing all the occurrences of a character with the given character. The replace() method of JDK 1.5 replaces the char and a sequence of char values.

Syntax:

These are the following two types of replace() methods in the Java String class.

public string replace(char prevChar, char newChar)
public String replace(CharSequence target, CharSequence replacement)

Parameters

prevChar: The parameter defines the character of the string to be replace.

newChar: The parameter defines the newChar that takes the place of the prevChar.

target: The parameter defines the target sequence of characters.

replacement: The parameter defines the replacement sequence of characters.

Let's take an example to understand how we can use the replace() method in Java programs.

ReplaceExample1.java

// import required classes and packages
package javaTpoint.JavaExample;
import java.util.Scanner;
// create class ReplaceExample1 to understand both type of replace() method
public class ReplaceExample1
{  
	// main() method start
	public static void main(String args[]){  
		// declare str1 str2, c, and subStr
		String str1, str2, targetStr, replacementStr;
		char prevChar, newChar;
		
		// create instance of Scanner class to take input string from user
		Scanner sc = new Scanner(System.in);
		// take 1st string from user
		System.out.println("Enter 1st string :");
		str1 = sc.nextLine();
		System.out.println("Enter 2nd string :");
		str2 = sc.nextLine();
		System.out.println("Enter the target string for 1st string :");
		targetStr = sc.nextLine();
		System.out.println("Enter the replacement string for 1st string :");
		replacementStr = sc.nextLine();
		System.out.println("Enter character which you want to replace in 2nd string :");
		prevChar = sc.next().charAt(0);
		System.out.println("Enter character which take place of :"+prevChar+" in 2nd string :");
		newChar = sc.next().charAt(0);
		sc.close();
		String replaceStr1 = str2.replace(prevChar, newChar);//replaces all occurrences of prevChar to newChar 
		System.out.println("String after replacing "+prevChar+" with "+newChar+" is: "+replaceStr1);
		String replaceStr2 = str1.replace(targetStr, replacementStr);//replaces all occurrences of targetStr with replacementStr 
		System.out.println("String after replacing "+targetStr+" with "+replacementStr+" is: "+replaceStr2);
	}
}  

Output:

String.replaceAll() Method

The replaceAll() method is similar to the String.replaceFirst() method. The only difference between them is that it replaces the sub-string with the given string for all the occurrences present in the string.

Syntax:

The syntax of the replaceAll() method is as follows:

Parameters

str: The parameter defines the sub-string that we need to replace in the string.

replacement: The parameter defines the replacement string that takes the place of the str.

Let's take an example to understand how we can use the replaceAll() method in our programs.

ReplaceExample3.java

// import required classes and packages
package javaTpoint.JavaExample;
import java.util.Scanner;
// create class ReplaceExample3 to understand replaceAll() method
public class ReplaceExample3
{  
	// main() method start
	public static void main(String args[]){  
		// declare str1 str2, subStr
		String str1, targetStr, replacementStr;
		// create instance of Scanner class to take input string from user
		Scanner sc = new Scanner(System.in);
		// take 1st string from user
		System.out.println("Enter 1st string :");
		str1 = sc.nextLine();
		System.out.println("Enter the target string for 1st string :");
		targetStr = sc.nextLine();
		System.out.println("Enter the replacement string for 1st string :");
		replacementStr = sc.nextLine();		
		sc.close();
		String replaceStr1 = str1.replaceAll(targetStr, replacementStr);//replaces all occurrences of targetStr to replacementStr 
		System.out.println("String after replacing "+targetStr+" with "+replacementStr+" is: "+replaceStr1);
	}
}

Output:

String.replaceFirst() Method

The replaceFirst() method is another method for replacing the substring. It replaces the sub-string with the given string. The replaceFirst() method replaces only the first occurrence of the sub-string.

Syntax:

The syntax of the replaceFirst() method is as follows:

Parameters

Str: The parameter defines the sub-string that we need to replace in the string.

Replacement: The parameter defines the replacement string that takes the place of the str.

Let's take an example to understand how we can use the replaceFirst() method in our programs.

ReplaceExample2.java

// import required classes and packages
package javaTpoint.JavaExample;
import java.util.Scanner;
// create class ReplaceExample2 to understand replaceFirst() method
public class ReplaceExample2
{  
	// main() method start
	public static void main(String args[]){  
		// declare str1 str2, subStr
		String str1, targetStr, replacementStr;
		// create instance of Scanner class to take input string from user
		Scanner sc = new Scanner(System.in);
		// take 1st string from user
		System.out.println("Enter 1st string :");
		str1 = sc.nextLine();
		System.out.println("Enter the target string for 1st string :");
		targetStr = sc.nextLine();
		System.out.println("Enter the replacement string for 1st string :");
		replacementStr = sc.nextLine();		
		sc.close();
		String replaceStr1 = str1.replaceFirst(targetStr, replacementStr);//replaces first occurrences of targetStr to replacementStr 
		System.out.println("String after replacing "+targetStr+" with "+replacementStr+" is: "+replaceStr1);
	}

Output: