抽象类、接口、多态总结之四

1、为抽象类实例化

abstract class AA{
    public abstract void print();
}
class BB extends AA{
    public void print() {
        System.out.println("hello");
    }
}

public class AbstractCaseDemo01 {

    public static void main(String[] args) {
        AA a = new BB();
        a.print();
    }

}

输出结果为：hello

2、为接口实例化

interface AA{
    public abstract void print();
}
class BB implements AA{
    public void print() {
        System.out.println("hello");
    }
}

public class InterfaceCaseDemo01 {
    public static void main(String[] args) {
        AA a = new BB();
        a.print();
    }
}

输出结果为：hello

3、抽象类的应用

abstract class Person{
    private String name;
    private int age;
    public Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
    public void say(){
        System.out.println(this.getContent());
    }
    public abstract String getContent();
}
class Student extends Person{
    private float score;
    public Student(String name,int age,float score){
        super(name, age);
        this.score = score;
    }
    public String getContent() {
        return super.getName() + ",,," + super.getAge() + ",," + this.score;
    }
}
class Worker extends Person{
    private float salary;
    public Worker(String name,int age,float salary){
        super(name,age);
        this.salary = salary;
    }
    public String getContent() {
        return super.getName() + ",,," + super.getAge() + ",,," + this.salary;
    }
    
}

public class AbstractCaseDemo02 {

    public static void main(String[] args) {
        Person per1 = null;
        Person per2 = null;
        per1 = new Student("zhangsan", 20, 99.0f);
        per2 = new Student("sili", 30, 3000.f);
        per1.say();
        per2.say();
    }
}

输出结果为：

zhangsan,,,20,,99.0
sili,,,30,,3000.0

4、能够接收子类对象的函数

abstract class Person{
    private String name;
    private int age;
    public Person(String name,int age){
        this.name = name;
        this.age = age;
    }
    public String getName() {
        return name;
    }
    public int getAge() {
        return age;
    }
    public void say(){
        System.out.println(this.getContent());
    }
    public abstract String getContent();
}
class Student extends Person{
    private float score;
    public Student(String name,int age,float score){
        super(name, age);
        this.score = score;
    }
    public String getContent() {
        return super.getName() + ",,," + super.getAge() + ",," + this.score;
    }
}
class Worker extends Person{
    private float salary;
    public Worker(String name,int age,float salary){
        super(name,age);
        this.salary = salary;
    }
    public String getContent() {
        return super.getName() + ",,," + super.getAge() + ",,," + this.salary;
    }
}

public class AbstractCaseDemo02 {
    public static void main(String[] args) {
        Person per1 = null;
        Person per2 = null;
        per1 = new Student("zhangsan", 20, 99.0f);
        per2 = new Student("sili", 30, 3000.f);
        fun(per1);
        fun(per2);
    }
    private static void fun(Person p) {
        p.say();
    }
}

输出结果：

zhangsan,,,20,,99.0
sili,,,30,,3000.0