super_ Subclass object memory structure_ Inheritance tree traceability

1. super（ Super ）“ Can be seen as ” Is a reference to a direct parent object . Can pass super To access methods and properties in the parent class that are overridden by subclasses .
2. Use super To call ordinary methods , Statement has no restricted position , It can be used casually in subclasses .
3. In a class , If the first sentence of the constructor is not called super(...) perhaps this(...); that Java By default super(), The meaning is to call the parameterless method of the parent class .

super Use of keywords ：

public class TestSuper1 {
    public static void main(String[] args) {
        new ChildClass().f();
    }
}
class FatherClass{
    public int value;
    public void f(){
        value = 100;
        System.out.println("FatherClass.value=" + value);
    }
}
class ChildClass extends FatherClass{
    public int value;
    public int age;
    public void f(){
        super.f();// Call the normal method of the parent class 
        value = 200;
        System.out.println("ChildClass.value=" + value);
        System.out.println(value);
        System.out.println(super.value);// Call member variable of parent class 

    }
    public void f2(){
        System.out.println(age);
    }
}

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Inheritance tree tracing ：

attribute / Method search order ：（ For example, find variables h）

1. Find out if there are any properties in the current class h
2. Backtrack each parent in turn , See if there is... In each parent class h, until Object
3. If not found , A compilation error appears .
4. The above steps , Just find h Variable , Then the process stops .

Constructor call order ：

The first sentence is always ：super(...) To call the constructor corresponding to the parent class . So the process is ： Go back up to Object, Then the initialization block and construction method executed downward in turn , Until the previous subclass .

notes ：

Static initialization block call order , The same as the order of constructor calls , Not in reuse .