Difference between a += 10 and a = a + 10 in java? [duplicate]

Answer 1

This is defined in the Java Language Specification, section 15.25.2. The salient part is:

A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T is the type of E1, except that E1 is evaluated only once.

That is, in your case the difference is the implicit type cast:

byte a = 100;
a += 1000;    // compiles
a = a + 1000; // doesn't compile, because an int cannot be assigned to a byte.