关于java基础中，接口里面父类的对象指向子类的引用

父类的引用指向子类的对象，它只能看的到父类的那些方法~　子类自身的方法看不到～～

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如：
interface Singer { //定义了一个接口，它属于特殊的抽象类，
方法不用去实现，叫它的子类去实现它的方法
Public void sing();
public void sleep();

}

class Student implements Singer {
private String name;
Student(String name) {
this.name = name;
}
public void study {
System.out.println("studying ,,,,");
}
public String getName() {
return name;
}

public void sing() {
System.out.println("student is sing");
}
public void sleep() {
System.out.println("student is sleep");
}
}

public class Test {
public static void main(String[] args) {
Singer s1 = new Student("le"); //父类的引用指向子类的对象
s1.sing(); s1.sleep();
}
}

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打印结果为:
student is singing (分析：因为new的s1这个对象只能看到子类中父类的方法，子类的方法是看不到的)
即父类的引用指向子类的对象
student is sleeping