【无标题】

package 继承与方法覆盖;

public class ExtendsTest {
    public static void main(String[] args){
        Animal u = new Animal();
        u.move();

        Dog u1 = new Dog();
        u1.move();

        Bird u2 = new Bird();
        u2.move();
    }

}

public class Animal {

    public void move(){
        System.out.println("动物在移动！");
    }
}

public class Dog extends Animal{

    public void move(){
        System.out.println("狗在狗叫！");
    }
}

public class Bird extends Animal{

    public void move(){
        System.out.println("大鸟在乱飞！");
    }
}

参数传递：

public class Test2 {
    public static void main(String[] args) {
        User u = new User(20);
        // User u = 0*1234;
        add(u);
        System.out.println("main->:"+u.i); //输出21
    }
    public static void add(User u){
        u.i++;
        System.out.println("add->:"+u.i); //输出21
    }
}
    class User{         //构造方法
        int i;
        public User(int i){
            this.i = i;
        }
    }

public class Test1 {
    public static void main(String[] args){
        int i = 10;
        add(i);
        System.out.println("main->:"+i); //输出10
    }
    public static void add(int i){
        i++;
        System.out.println("add->:"+i); //输出11
    }
}