types - Why Doesn't Java Allow Casting Boolean -> Int? - Stack Overflow

It doesn't allow this because the Java designers (correctly) recognized that the boolean / integer overloading in C and C++ was a significant source of errors.

(I recall seeing that in writing in some design rationale, but I can't find it.)

For instance:

if (i = 0) {      ...  }

is legal but probably a bug in C or C++.

Java avoid this and other problems by making boolean and the integer datatypes different types that cannot be converted from one to the other. Thus, the above is a compilation error in Java.

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Now this doesn't explain why you cannot explicitly type cast a boolean to an int. But I think that can be understood by observing the following:

• You rarely need to do that in real Java programs.

• Number <-> boolean casting wouldn't jell with the way that other type casts work. In particular, for other types there are up-casts and down-casts, and up-casts in Java don't require an explicit type cast.

• You can't typecast between numbers and string either, or between strings an other objects. These are conversion, not type casts. And in <-> boolean is too.

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