数组中存放引用类型分析

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public class Test01 {
public static void main(String[] args) {
Cat c = new Cat();
Bird b = new Bird();
Animal[] a = { c, b };
for (int i = 0; i < a.length; i++) {
if (a[i] instanceof Cat) {
// 调用子类方法需要强制向下转型
// 不能直接调用会报错
Cat cat = (Cat) a[i];
cat.catchmouse();
} else if (a[i] instanceof Bird) {
Bird bird = (Bird) a[i];
bird.sing();
}
}
}
}

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class Animal {
public void move() {
System.out.println("Animal move..");
}
}
class Cat extends Animal {
public void move() {
System.out.println("cat is walking");
}
public void catchmouse() {
System.out.println("cat can catch mouses");
}
}
class Bird extends Animal {
public void move() {
System.out.println("bird is flying");
}
public void sing() {
System.out.println("bird is sing");
}
}

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cat can catch mouses
bird is sing

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当我们在数组中存放引用数据类型时，想要调用子类的方法，我们需要先
采用instanceof对“对象”进行类型判断，再强制向下转型才可以进行调用。
当我们调用数组中引用的共有方法时，可直接调用，例如：调用a.move()方法

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public static void main(String[] args) {
Cat c = new Cat();
Bird b = new Bird();
Animal[] a = { c, b };
for (int i = 0; i < a.length; i++) {
a[i].move();
if (a[i] instanceof Cat) {
// 调用子类方法需要强制向下转型
// 不能直接调用会报错
Cat cat = (Cat) a[i];
cat.catchmouse();
} else if (a[i] instanceof Bird) {
Bird bird = (Bird) a[i];
bird.sing();
}
}
}

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程序输出

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cat is walking
cat can catch mouses
bird is flying
bird is sing