equals和==小测试

package testSingle;

import org.junit.Test;

public class TestEqualSingle
{
    @Test
    public void testSingle()
    {
        Person p = Person.getInstanse();
        Person p1 = Person.getInstanse();
        System.out.println(p1 == p);// true
    }
    /**总结：单例模式产生的对象是同一个对象，==意味着引用的对象是同一个，
     * 不管改引用对象是在堆里还是栈里 .*/
    @Test
    public void testEqules()
    {
        Person p = Person.getInstanse();
        Student s = new Student();
        s.setName("张三");
        System.out.println(s.equals(p));// true
    }
    /**
     * 总结：然后是equals方法相等，它不管是什么类的对象，只管
     * 是否符合能够让equals相等,当你没重写hashcode方法时，不会相等，
     * 因为Object写的 hashcode是随机的，equals相等的前提条件是hashcode相同
     */
}

class Student
{
    private String name;
    
    public String getName()
    {
        return name;
    }
    
    public void setName(String name)
    {
        this.name = name;
    }
    
    @Override
    public boolean equals(Object obj)
    {
        if (obj instanceof Student)
        {
            Student s = (Student)obj;
            if (s.getName() != null)
            {
                return s.getName().equals(this.name);
            }
        }
        if (obj instanceof Person)
        {
            Person p = (Person)obj;
            if (p.getName() != null)
            {
                return p.getName().equals(this.name);
            }
        }
        return false;
    }
    
    @Override
    public int hashCode()
    {
        return this.name.hashCode();
    }
}

class Person
{
    private String name;
    
    private static final Person per = new Person();
    
    /** 获取单例 */
    public static Person getInstanse()
    {
        return per;
    }
    
    private Person()
    {
        super();
        name = "张三";
    }
    
    @Override
    public int hashCode()
    {
        return this.name.hashCode();
    }
    
    @Override
    public boolean equals(Object obj)
    {
        if (obj instanceof Student)
        {
            Student s = (Student)obj;
            if (s.getName() != null)
            {
                return s.getName().equals(this.name);
            }
        }
        if (obj instanceof Person)
        {
            Person p = (Person)obj;
            if (p.getName() != null)
            {
                return p.getName().equals(this.name);
            }
        }
        return false;
    }
    
    public String getName()
    {
        return name;
    }
    
    public void setName(String name)
    {
        this.name = name;
    }
    
}