Java深入讲解instanceof关键字的使用

public class Person extends Object {…}
public class Student extends Person {…}
public class Graduate extends Person {…}
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public void method1(Person e) {
   if (e instanceof Person) {// 处理Person类及其子类对象}   
   if (e instanceof Student) {//处理Student类及其子类对象}
   if (e instanceof Graduate){//处理Graduate类及其子类对象}
}

public class ConversionTest {
   public static void main(String[] args) {
     double d = 13.4;
     long l = (long) d;
     System.out.println(l);//13
     int in = 5;
     // boolean b = (boolean)in;
     Object obj = "Hello";
     String objStr = (String) obj;
     System.out.println(objStr);//Hello
     Object objPri = new Integer(5);
     // 所以下面代码运行时引发ClassCastException异常
    String str = (String) objPri; 
    /*
    Exception in thread "main" java.lang.ClassCastException:          
    java.lang.Integer cannot be cast to java.lang.String
    */
    } 
}

class Person {
	String name;
	int age;	
	int id = 1001;	
	public void eat(){
		System.out.println("人：吃饭");
	}	
	public void walk(){
		System.out.println("人：走路");
	}	
}
class Man extends Person{	
	boolean isSmoking;	
	int id = 1002;	
	public void earnMoney(){
		System.out.println("男人负责挣钱养家");
	}	
	public void eat(){
		System.out.println("男人多吃肉，长肌肉");
	}	
	public void walk(){
		System.out.println("男人霸气的走路");
	}
}
class Woman extends Person{	
	boolean isBeauty;	
	public void goShopping(){
		System.out.println("女人喜欢购物");
	}	
	public void eat(){
		System.out.println("女人少吃，为了减肥");
	}	
	public void walk(){
		System.out.println("女人窈窕的走路");
	}
}
public class PersonTest {
	public static void main(String[] args) {
//问题一：编译时通过，运行时不通过
		//举例一：
//		Person p3 = new Woman();
//		Man m3 = (Man)p3;
		//举例二：
//		Person p4 = new Person();
//		Man m4 = (Man)p4;
		//问题二：编译通过，运行时也通过
//		Object obj = new Woman();
//		Person p = (Person)obj;
		//问题三：编译不通过
//		Man m5 = new Woman();		
//		String str = new Date();		
//		Object o = new Date();
//		String str1 = (String)o;
	}
}