When creating a derived class object, what is the execution order of constructors?

When creating a derived class object, the execution order of the constructor is: base class constructor, derived class object member constructor, and the constructor of the derived class itself. When an object is created, the code loading order is: static code, non-static code, and constructor methods.

When creating a derived class object, the execution order of the constructor is: base class constructor, derived class object member constructor, and the constructor of the derived class itself.

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Detailed introduction:

The loading order of the code when the object is created is: static code --> Non-static code --> Constructor.

If the parent class is inherited, the loading order is: the static code of the parent class --> the static code of the subclass --> the non-static code within the parent class --> the parent class's Constructor --> Non-static code of the subclass --> Constructor of the subclass.

Among them, static code includes (static methods, static variables, static code blocks, etc.), non-static code is (member methods, member variables, member code blocks, etc.). The same type of code, written above load.

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Example:

public class ExtendsTest {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		C c = new D();
	}

}

class C {
	static {
		System.out.println("C 基类静态域 ");
	}
	{
		System.out.println("C 基类对象成员构造函数");
	}

	public C() {
		System.out.println("C 基类本身的构造函数");
	}
}

class D extends C {
	static {
		System.out.println("D 派生类静态域");
	}
	{
		System.out.println("D 派生类对象成员构造函数");
	}

	public D() {
		System.out.println("D 派生类本身的构造函数");
	}
}

Output result:

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