Query Regarding the below code snippet

Question

public static void main(String args[]) throws IOException
    {
        String s1="abc";
        String s2="xyz";
        String s3="abcxyz";

        String s4=s1.concat(s2);
        System.out.println(s4);
        @SuppressWarnings("unused")
        String s5=s1+s2;

        if(s3==s4)
        {
            System.out.println("true");
        }
        else
            System.out.println("false");
    }

Why the o/p is coming as false? According to me it should be true. Can someone please explain

== checks for reference,if you want to check for data then use .equals() — SpringLearner, Oct 12 '15 at 05:27

score -1 · Answer 1 · answered Oct 12 '15 at 05:26

java.lang.String concat() function return new String() object Here s3 and s4 are two different references pointing to two different objects.

== just checks for refernces wheras .equals() checks for the actual content.

s3.equals(s4) will return true.

From javadoc, concat() function.

 public String concat(String str) {
        int otherLen = str.length();
        if (otherLen == 0) {
            return this;
        }
        int len = value.length;
        char buf[] = Arrays.copyOf(value, len + otherLen);
        str.getChars(buf, len);
        return new String(buf, true);
    }

score -1 · Answer 2 · edited Oct 27 '15 at 13:18

-1

== operator compares String value as well as String memory location. Here, s3 and s4 are using different memory locations.

If you want to compare values of String then you should use s3.equals(s4). It will result into true condition.

edited Oct 27 '15 at 13:18

Chirag Soni

437
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answered Oct 12 '15 at 05:27

Kruti Patel

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Query Regarding the below code snippet

2 Answers2