Identical strings comparison gives me false [duplicate]

This question already has answers here: 开发者_运维问答 How do I compare strings in Java? (23 answers) Closed 6 years ago.

I have two identical strings, one in an array and one in a String variable. When I compare these IDENTICAL strings I get false every time. I have debugged and debugged, but I get the same result every time. Here is the code in question

String temp = ""+(num1*num2);
Boolean equal = temp == answers[i];

if(equal) {
    correct[i] = true;
    num_correct ++;
}else{
    correct[i] = false;
}

Again, I have debugged every minor detail of this program and I am 101% sure that the strings are IDENTICAL. Why is Java returning false on comparison?

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When you use the == operator in Java with objects, you are attempting to compare object references. That is, is this object handle pointing to the EXACT same object as this other object handle. Unless the strings are interned, this will not work.

Use String.equals(Object) instead:

Boolean equal = temp.equals(answers[i]);

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You are doing reference comparison, not value comparison. When you use the == operator its checking to see if the references are equal, and they aren't. If you want to check whether the values are equal use the equals method.

boolean equal = temp.equals(answers[i]);

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== in java for strings is comparing to see if they are the same object, not the same string value. You should use .equals instead which will compare the value. == works sometimes because the strings can be interned and refer to the same object via reference even if created seperately through the same literal (so string b = "Hey" and string c = "Hey" end up being the same object in the background because "Hey" got interned to a hidden string object).

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As others have shown you should use equals.

But I would also use the booleanValue of the Boolean object.

Here is your code correctly done

String temp = ""+(num1*num2);
Boolean equal = temp.equals(answers[i]);

if(equal.booleanValue()) {
    correct[i] = true;
    num_correct ++;
}else{
    correct[i] = false;
}

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Does this help?

Boolean equal = (temp == answers[i]);

I'm not sure that would be an issue, but I always enclose my conditions in parenthesis.