Question

Possible Duplicate:
Varying behavior for possible loss of precision

Code Sample A

 public class Test {                                                         
     public static void main(String[] args) {
         int i = 0;
         i = i + 1.5;
     }
 }

Code Sample B

 public class Test {                                                         
     public static void main(String[] args) {
         int i = 0;
         i += 1.5;
     }
 }

Unsurprisingly, compiling A produces the error below. Surprisingly, compiling B produces no error and it appears to behave as if I inserted an explicit cast to integer before the double value 1.5. Why in the world does this happen? This goes against everything I thought I knew!

Test.java:6: possible

 loss of precision

    found   : double
    required: int
            i = i + 1.5;
                  ^
    1 error

Answer 1

It is working as designed. The compound operators add an implicit cast to the operation. Otherwise you have to use an explicit cast.

More info?

http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.26.2