Why boolean in Java takes only true or false? Why not 1 or 0 also?

Question

Is there any reason why Java booleans take only true or false why not 1 or 0 also?

Answer 1

One thing that other answers haven't pointed out is that one advantage of not treating integers as truth values is that it avoids this C / C++ bug syndrome:

int i = 0;
if (i = 1) {
    print("the sky is falling!\n");
} 

In C / C++, the mistaken use of = rather than == causes the condition to unexpectedly evaluate to "true" and update i as an accidental side-effect.

In Java, that is a compilation error, because the value of the assigment i = 1 has type int and a boolean is required at that point. The only case where you'd get into trouble in Java is if you write lame code like this:

boolean ok = false;
if (ok = true) {  // bug and lame style
    print("the sky is falling!\n");
}

... which anyone with an ounce of "good taste" would write as ...

boolean ok = false;
if (ok) {
    print("the sky is falling!\n");
}