【Java】hashcode()和equals()

大家知道，在集合中判断集合中的两个元素是否相同，依赖的是hashcode()和equals()两个方法。

 

> 一个简单的实验

public class Teacher {
    
    private Integer id = null;

    public Teacher(Integer id) {
        super();
        this.id = id;
    }

    @Override
    public String toString() {
        StringBuilder builder = new StringBuilder();
        builder.append("Teacher [>);
        return builder.toString();
    }
    
    /*
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Teacher other = (Teacher) obj;
        if (id == null) {
            if (other.id != null)
                return false;
        } else if (!id.equals(other.id))
            return false;
        return true;
    }
    */
    
}

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