Why my contains and replace method doesn't work right? [duplicate]

Question

This question already has answers here:

Why isn't the String value changed after String.Replace in Java? [duplicate] (6 answers)

Closed 7 years ago.

I was trying to make something then i couldn't write an if method with contains and replace method. What was i missing?

   import java.util.Scanner;
public class replacesomething
{
    public static void main(String[] args)
    {
        Scanner cumle = new Scanner(System.in);
        System.out.println("Enter the sentence u want to replace ");
        String str1 = cumle.next();
        if (str1.contains("replace"))
        {
            str1.replace("replace", "Hi");
            System.out.println("Replaced Sentence: " + str1);
        }
        else
        {
            System.out.println("Sentence doesn't contains that...");
        }

    }

}

Answer 1

Change the replace method call to:

str1 = str1.replace("replace", "Hi");

Since String are immutable, you need to reassign the result back to str1. It doesn't perform in-place replacement, rather it constructs and returns a new String object. the original String is unmodified.

Answer 2

Strings are immutable in Java; you can't edit them once created. Instead, the "replace" method returns an new string. If you assign str1 with the result of replace you will get the result you expect.