java 期末考试复习

Posted 2021-01-25 排序和map

inheritance

? Constructors are inherited, but use super() 

 

public class Parent { public Parent() {
do some code; }
}
public class Child extends Parent {
public Child() {
super(); // call Parent() do some more code;
} }
so in a main method:
Child c = new Child(); // Calls Parent(), too

 

Default constructor == no parameters 

第72页，子类能加新方法吗？

 

只有public方法的可以override，别的几个关键字都不行