JQ + Question ID :958011966030

[huiying li]

public class Test34
{
    public static void main(String args[])
    {
        System.out.println(null + true); //1
        System.out.println(true + null); //2
        System.out.println(null + null); //3
    }
}

The answer given is none of the three lines will compile, however, using JDK 1.3, all three did compile and here are the output.

C:\JavaRanch>javac Test34.java
C:\JavaRanch>java Test34
nulltrue
truenull
nullnull
Any thoughts?

[Subramaniam Venkatesan]

None of the 3 lines compiled in jdk1.2.2
got these errors

C:\subs\SAMPLES>javac Test34.java
Test34.java:7: Reference to println is ambiguous. It is defined in void println(
java.lang.String) and void println(char[]).
System.out.println(null);
                  ^

C:\subs\SAMPLES>javac Test34.java
Test34.java:7: Incompatible type for +. Can't convert boolean to int.
System.out.println(true+null);
                       ^
Test34.java:7: Incompatible type for +. Can't convert null to int.
System.out.println(true+null);

but got truenull or the o/p you mentioned
in these codes

        System.out.println(null + ""+ true); //1
        System.out.println(true + ""+null); //2
        System.out.println(null + ""+ null); //3

[Stevie Kaligis]

Yes,
I was about to ask the same question,
it suppose to be compiled and run without any problem,
if this topic is related to JDK 1.0 and 1.1, than JQPlus was right,
but for JDK 1.2 and 1.3, it works without any problem.

[huiying li]

Thanks for your replies, hopefully there won't be something ambiguous like this in the real test.