Java String replace() Method

In Java, we can replace occurrences of a character or substring using the replace() method, which has two variations:

1. replace(char oldChar, char newChar)
2. replace(CharSequence oldString, CharSequence newString)

These methods return a new string with the replacements made. Note that the original string is not modified since strings in Java are immutable.

Syntax

The replace() method in Java has two syntaxes.

• 1. Syntax for Replacing a Character:

• 2. Syntax for Replacing a Substring:

Parameters Values

To replace all occurrences of a particular character with another character in Java, we use the first syntax of the replace() method in Java.

1. oldChar - The character to be replaced in the string.
2. newChar - The character to be used instead of oldChar in the string.

To replace all occurrences of a particular string or substring with another string or substring, we use the second syntax of the replace() method in Java.

1. oldString - The string or substring to be replaced in the original string.
2. newString - The string or substring to be used in place of the old string or substring in the original string.

Return Value

The replace() method in Java returns a new string where each occurrence of a character/word/sentence has been replaced with a new character/word/sentence.

If there is no match for the new character/word/sentence, the replace() in Java method returns the original string.

Exception

We cannot use null as an argument in the replace() method. If we use null as an argument, the system will throw a NullPointerException.

Internal Implementation

Here is the internal implementation of the replace method in Java:

Java String replace() Method Examples

Example 1: Java String replace(char old, char new) Method

Replacing One Character with Another in Java Using replace() in java.

Output:

In the above code, we display the string object "G00d M0rning" and then call the replace() method on this object. We replace '0' with 'o' and then print the modified string on the screen.

Example 2: Java String replace(CharSequence target, CharSequence replacement) Method

Example of the replace(CharSequence oldString, CharSequence newString) method in Java:

Output:

Exception 3: Exception in Java replace() method

Output