我定义了一个teacher类
private String name;
private int age;//下面是自动生成的hashCode
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
result = prime * result + age; //result的值肯定会被下面的覆盖掉
result = prime * result + ((name == null) ? 0 : name.hashCode());
为什么这么写。
private String name;
private int age;//下面是自动生成的hashCode
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + age;
result = prime * result + ((name == null) ? 0 : name.hashCode());
return result;
}
result = prime * result + age; //result的值肯定会被下面的覆盖掉
result = prime * result + ((name == null) ? 0 : name.hashCode());
为什么这么写。
result = prime * result + ((name == null) ? 0 : name.hashCode());
注意到这句话中,result也参与了计算,而且放大了31倍。结合之前的计算,两句话合并相当于是:
result = prime * (prime * result + age) + ((name == null) ? 0 : name.hashCode());
代入数字的话也即:
return 31 * (31 + age) + ((name == null) ? 0 : name.hashCode());