java_object

class  extends Object
{
	private int age = 0 ;
	Person(int age)
	{
		this.age = age;
	}
  
	public boolean equals(Object obj)
	{
		if (!(obj instanceof Person))
		{
			throw new ClassCastException("类型转换错误");
		}
		Person p = (Person)obj;
		return this.age == p.age;
	}
	public int hashCode()
	{
		return age;
	}
}
class Demo
{
}
class ObjectDemo
{
	public static void main(String[] args)
	{
		Person p1 = new Person(20);
		Person p2 = new Person(20);
		Person p3 = p1;
		Demo d = new Demo();
    // equals()
		System.out.println(p1==p2);
		System.out.println(p1.equals(p2));
		System.out.println(p1.equals(p3));
		System.out.println(p1.equals(d));
    // hashCode()
		System.out.println(p1);//打印对象就是打印对象的hash码
		System.out.println(Integer.toHexString(p1.hashCode()));
    // getClass()
		Class c1 = p1.getClass();
		Class c2 = p1.getClass();
		System.out.println(c1==c2);//一个Person.class字节码文件，内存中只有一份，但可以创建多个对象，c1,c2都是Class的对象
		System.out.println(c1.getName());
    // toString()
		System.out.println(p1);
		System.out.println(p1.getName()+"$"+Integer.toHexString(p1.hashCode()));
	}
}

false
true
true
ClassCastException:类型转换错误
[email protected]3c
3c
true
Person

public boolean equals(Object obj)
{
	return (this == obj);
}