Using str1==str2 in System.out.println prints only true or false but does not print any text written along with it

Question

Here is what i am talking about:

package finalExample;

public class FinalExample {

public static void main(String args[]) {

    final String str1 = "str";
    final String str2 = "ing";

    String str11 = "str";
    String str22 = "ing";

    System.out.println("Using equals() for non final :" + str11.equals(str22));
    System.out.println("Using == for non final :" + (str11==str22));
    System.out.println("MAGIC Using == for non final :" + str11==str22);

    System.out.println("Using equals() for final :" + str1.equals(str2));
    System.out.println("Using == for final :" + (str1==str2));
    System.out.println("MAGIC Using == for final :" + str1==str2);
}

}

Output is:

Using equals() for non final :false
Using == for non final :false
false
Using equals() for final :false
Using == for final :false
false

Both MAGIC Statements are not printed. Why is it so?

Actually, I deleted my answer. Based on the "tricky" nature of the question and the name of the class, this sounds suspiciously like a homework question... — yshavit, Oct 17 '13 at 06:26
@yshavit no it is not a homework question bro. I came across this all of a sudden while working, and i wanted to ask the reason so i wrote this example class and posted here. — Destructor, Oct 17 '13 at 06:29
Alright, then cool and sorry to be suspicious. We get that a lot on SO, unfortunately. :( — yshavit, Oct 17 '13 at 06:31
@Claudiu not exactly ! I know why are final and non final acting that way, but i wanted to know why is the MAGIC statement not printing. Still thanks for the link. :) — Destructor, Oct 17 '13 at 06:31
[Operator Precedence](http://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html) — Aniket Kulkarni, Oct 17 '13 at 06:33

chrylis -cautiouslyoptimistic- · Accepted Answer · 2013-10-17T06:32:49.327

12

The + operator binds at a higher precedence than the == operator, so your expression is:

"MAGIC Using == for final :" + str1==str2
("MAGIC Using == for final :" + str1)==str2
(a new String object created for the comparison can't)==str2
false

edited Oct 17 '13 at 06:32

answered Oct 17 '13 at 06:25

chrylis -cautiouslyoptimistic-

75,269
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score 3 · Answer 2 · answered Oct 17 '13 at 06:25

3

You are evaluating

"MAGIC Using == for non final :" + str11

which is a string, and then comparing with str2

answered Oct 17 '13 at 06:25

djna

54,992
14
74
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score 2 · Answer 3 · answered Oct 17 '13 at 06:29

2

I think it did print. the result is false; so it prints "false" you can think it as: res = "MAGIC Using == for final :" + str1 ; println(res == str2) so it prints false.

answered Oct 17 '13 at 06:29

Robin

134
9

Using str1==str2 in System.out.println prints only true or false but does not print any text written along with it

3 Answers3