HashCode

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hashCode 和equals 什么时候hashCode的值会相等？两者之间有什么关系？

Character c=new Character('3');

String d=new String("3");

Character a=new Character(c);

String b=new String(d);

System.out.println("a.equals(b)="+a.equals(b));

System.out.println("c.equals(d)="+c.equals(d));

System.out.println("a.hashCode()="+a.hashCode());

System.out.println("b.hashCode()="+b.hashCode());

System.out.println("c.hashCode()="+c.hashCode());

System.out.println("d.hashCode()="+d.hashCode());

运行结果：

a.equals(b)=false

c.equals(d)=false

a.hashCode()=51

b.hashCode()=51

c.hashCode()=51

d.hashCode()=51

String c=new String("3");

String d=new String("3");

String a=new String(c);

String b=new String(d);

System.out.println("a.equals(b)="+a.equals(b));

System.out.println("c.equals(d)="+c.equals(d));

System.out.println("a.hashCode()="+a.hashCode());

System.out.println("b.hashCode()="+b.hashCode());

System.out.println("c.hashCode()="+c.hashCode());

System.out.println("d.hashCode()="+d.hashCode());

运行结果：

a.equals(b)=true

c.equals(d)=true

a.hashCode()=51

b.hashCode()=51

c.hashCode()=51

d.hashCode()=51

/代码

Integer c=new Integer('3');
String d=new String("3");
Integer a=new Integer(c);
String b=new String(d);
System.out.println("a.equals(b)="+a.equals(b));
System.out.println("c.equals(d)="+c.equals(d));
System.out.println("a.hashCode()="+a.hashCode());
System.out.println("b.hashCode()="+b.hashCode());
System.out.println("c.hashCode()="+c.hashCode());
System.out.println("d.hashCode()="+d.hashCode());
}
}

//运行结果：

a.equals(b)=false
c.equals(d)=false
a.hashCode()=51
b.hashCode()=51
c.hashCode()=51
d.hashCode()=51

//代码

Integer c=new Integer(3);
String d=new String("3");
Integer a=new Integer(c);
String b=new String(d);
System.out.println("a.equals(b)="+a.equals(b));
System.out.println("c.equals(d)="+c.equals(d));
System.out.println("a.hashCode()="+a.hashCode());
System.out.println("b.hashCode()="+b.hashCode());
System.out.println("c.hashCode()="+c.hashCode());
System.out.println("d.hashCode()="+d.hashCode());

//运行结果：

a.equals(b)=false
c.equals(d)=false
a.hashCode()=3
b.hashCode()=51
c.hashCode()=3
d.hashCode()=51

总结:equals=true hashCode相等；hashCode相等 equals不一定=true

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