关于继承

方法可覆盖，变量不可覆盖，引用是父类，实例是子类，那么变量用父类的，方法用子类的

class father { int num = 5; public void call() { System.out.println("father"); } } class son extends father { int num = 9; public void call() { System.out.println("son"); } } public class a { public static void main(String[] args) { father b=new son(); System.out.println(b.num); b.call(); } }

以上输出：

5

son

 

若方法调用了变量，那么调用的是方法所在类中的变量

class father { int num = 5; public void call() { System.out.println(num); } } class son extends father { int num = 9; public void call() { System.out.println(num); } } public class a { public static void main(String[] args) { father b=new son(); System.out.println(b.num); b.call(); } }

以上输出：

5

9

class father { int num = 5; public void call() { System.out.println(num); } } class son extends father { int num = 9; } public class a { public static void main(String[] args) { father b=new son(); System.out.println(b.num); b.call(); } }

以上输出：

5

5