Java hashCode，等于错误我不明白[重复]

Question

我必须在我的班级中重写 hashCode 方法，但我有这个错误：

找不到符号：符号：变量对象

另外，我如何在 equals 中添加字符串发明者比较 我的代码：

public abstract class ThingMadeByHuman {

    protected String inventor;
    protected int yearOfInvention;

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o != null || getClass() != o.getClass()) {
            return false;
        }
        ThingMadeByHuman thingMadeByHuman = (ThingMadeByHuman) o;
        return Integer.compare(thingMadeByHuman.yearOfInvention, yearOfInvention) == 0;
    }

    @Override
    public String toString() {
        return "ThingMadeByHuman: inventor:" + this.inventor + " yearOfInvention:" + this.yearOfInvention;
    }

    @Override
    public int hashCode() {
        return Objects.hash(yearOfInvention) + super.hashCode();
    }

    public ThingMadeByHuman(String inventor, int yearOfInvention) {
        this.yearOfInvention = yearOfInvention;
        this.inventor = inventor;
    }
}

Answer 1

您可能需要导入Objects 类。请参阅 Java docs。请参阅 Oracle 的 tutorial。

import java.util.Objects ;