java中的instanceof关键字详细解读

public static void main(String[] args) {
        Dog dog = new Dog();
        Animal animal = new Animal();
        Animal cat = new Cat();
        System.out.println("dog instanceof Dog的结果是：" + (dog instanceof Dog));     // true
        System.out.println("dog instanceof Big的结果是：" + (dog instanceof Big));    // true
        System.out.println("animal instanceof Big的结果是：" + (animal instanceof Big)); // true
        System.out.println("animal instanceof Dog的结果是：" + (animal instanceof Dog));  // false
        System.out.println("cat instanceof Animal的结果是：" + (cat instanceof Animal));  // true
        System.out.println("cat instanceof Cat的结果是：" + (cat instanceof Cat));     // true
    }

  Dog[] dog = new Dog[3];
Animal animal = new Animal();
System.out.println("dog instanceof Dog[]的打印结果是："+(dog instanceof Dog[]));   
System.out.println("dog instanceof Big[]的打印结果是："+(dog instanceof Big[])); 

int[] arr = new int[3];
System.out.println("arr instanceof int[]的打印结果是："+(arr instanceof int[]));

/**
 *========================================
 * @方法说明 ： 空判断 空返回true
 * @param   obj
 * @return      boolean
 * @exception
 *========================================
 */
public static boolean isEmpty(Object obj) {
    if (obj == null || "null".equals(obj.toString()) || "".equals(obj.toString())) {
        return true;
    }
    if (obj instanceof String) {
        return ((String) obj).trim().length() == 0;
    }
    if (obj instanceof Collection) {
        return ((Collection) obj).isEmpty();
    }
    if (obj instanceof Map) {
        return ((Map) obj).isEmpty();
    }
    return false;
}