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(This question may be a duplicate but I really didn't understand the other answers)

You have the following code:

String str ="football";
str.concat(" game");
System.out.println(str); // it prints football

But with this code:

String str ="football";
str = str + " game";
System.out.println(str); // it prints football game

So what's the difference and what's happening exactly?

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  • 2
    You didn't assign str.concat(" game"); to a variable, so str still has its original value. Commented May 31, 2018 at 14:44
  • Strings are imutable, so you have to assing str.concat(" game"); to a variable Commented May 31, 2018 at 14:46

2 Answers 2

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str.concat(" game"); has the same meaning as str + " game";. If you don't assign the result back somewhere, it's lost. You need to do:

str = str.concat(" game");
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2 Comments

So what happened exactly is the following? : str.concat(" game") created a new string object "football game" But it didn't change the str reference, and str still refer to "football"
@BaselQarabash yes
2

The 'concat' function is immutable, so the result of it must be put in a variable. Use:

str = str.concat(" game");
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1 Comment

Just a small thing: Strings are imutable, not the concat function

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