this and super
this 和 super 的区别:this, 先从本类找属性和方法,本类找不到再从父类找。super, 从父类找。
this 和 super 都可以调用构造方法,所以this() 和 super() 不可以同时出现。
public class Person { }
public class Student extends Person { String name; public Student(String name) { super(); // this(); } public Student() {} }
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
class FatherClass { public int value; public void f() { value = 100; System.out.println("FatherClass,value = " + value); } } class ChildClass extends FatherClass { public int value; public void f() { super.f(); value = 200; System.out.println("ChildClass,value = " + value); System.out.println(value); System.out.println(super.value); } } public class Demo { public static void main(String[] args) { ChildClass cc = new ChildClass(); cc.f(); } }
画图分析:
问题:
class Person { public String name; public String location; Person (String name) { this.name = name; location = "beijing"; } Person (String name, String location) { this.name = name; this.location = location; } public String info() { return "name:" + name + ",location:" + location; } } class Student extends Person { private String school; Student(String name, String school) { // 这个地方应该调用父类无参的构造方法,但父类没有无参的构造方法,但实际上并没有调用,下面的"xxx"可以打印出来。? this(name, "benjing",school); } public Student(String name, String location, String school) { super(name, location); this.school = school; } } public class Demo { public static void main(String[] args) { new Student("c", "s1"); System.out.println("xxx"); } }