Declaring a method when creating an object

Question

Why first way is correct, but second isn't?

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First way:

new Object() {     public void a() {         /*code*/     } }.a(); 

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Second way:

Object object = new Object() {     public void a() {         /*code*/     } };  object.a(); 

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And where can I find more information about it?

Answer 1

java.lang.Object has no a methods declared (2), while the anonymous class returned by the class instance creation expression new Object() { public void a() {} } does (1).

Use Java 10's local variable type inference (var) to make the second option as valid as the first one.

var object = new Object() {     public void a() {} }; object.a();