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Programming in Java Netbeans - A Step by Step Tutorial for Beginners: Lesson 24

Updated on October 16, 2019
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Danson Wachira is a certified Trainer in Computer Science, Information Technology and related studies.

Lesson 24: How to use replace() method in Java

When working with values of string type as a programmer, you may need a function to find a character or group or characters in a given string and replace them with other characters.

Java has inbuilt methods that can be used to replace a character or a group of characters with other characters in a string. The particular method we shall discuss here is replace() method.The syntax of using replace() method in Java is shown below:

Original_string.replace(find_string, replace_string);

Source

The original string comes first before the replace() method, inside the brackets, you first put the string to find then the string that you need to replace. These two strings in the brackets must be separated by a comma.

Replace function can be used in many applications especially when one want to change a single word or several words in a paragraph or document. The replace function has been used in many word processing applications.

Remember the “Find and Replace” function provided in Microsoft Word application? Take a look on the image below:

“Find and Replace” function in Microsoft Word 2010 application

Now, suppose we have a sentence that has a word that we need to find and replace. Let us use the example of a sentence given below:

Java is an object oriented language

In the above sentence, we want to replace the word “language” with “programming language.” Using the Java replace() method, let us write a program to find and replace characters, word or words in a sentence or paragraph. Copy and paste or type the code shown below.

Java program using replace() method

package myfirstprogram;
import javax.swing.JOptionPane;
public class Replace {
     public static void main(String[] args) {
      String sentence = "Java is an object oriented language";
      String findString;
      String replaceString;
      String amend;
      
      //Display string before changes
      JOptionPane.showMessageDialog( null,"Original sentence: "+sentence);
      
      //Find string to replace
      findString = JOptionPane.showInputDialog("Find what:");
      
      //Provide replacement string
      replaceString = JOptionPane.showInputDialog("Replace with:");
      
      //Replace and store the new string in variable 'amend'
      amend = sentence.replace(findString, replaceString);
      
      //Display final string
      JOptionPane.showMessageDialog( null,"Final sentence: "+amend);
   }
}

Java replace() method has many variations as shown on the image below, try the different variations and test what each will produce.

Java has many useful inbuilt methods and I recommend that you check on the others that we have not discussed in this tutorial and also practice on how to use them. In the next lesson, we shall learn how we can write our own methods in Java programming language.

<< Lesson 23 | Lesson 25 >>

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