如果构造函数被声明为不完整类型会怎样？

Question

Just being curious. Having the following simple class:

public class Foo {
   private static int fooVar = 1;
   private int foo;
   private int boo = 1; // another int, not a typo
   public Foo(int foo) {
      this.foo = foo;  
   }
}

Calling:

Foo a, b, c;

Which one is declared first? (I assume from the lft to the right.) Are instance variables fooVar and foo declared too? What happens in the memory? Is the value of variable boo saved in the memory even the constructor haven't been called at all?

Answer 1

Nikolas,

a,b and c are pointers of type Foo. They should be, as you said, declared from left to right.

because is the same as declaring

Foo a;

Foo b;

Foo c;

What happens in the memory? Is the value of variable boo saved in the memory even the constructor haven't been called at all?

There is no such value boo or foo (typo?).

If the constructor has not been called, there is no object yet in your code.

If do this:

Foo a= new Foo();

You are actually doing 2 things, in the following order: First a Foo object is created, then it is a asigned to Foo pointer a.

Remember your constructor is like a method. Please add () before { And if you are passing a input variable, please do so inside the () like:

public Foo(foo) {
      this.foo = foo;  }