自己编写HashCodeBuilder类

jakarta-commons-lang已经实现了HashCodeBuilder类，据闻在Hibernate中出错，所以还是选择了自己实现，编码思想来源于 Effective java 一书。而且0依赖。

java 代码

import java.lang.reflect.Array;

public class HashCodeBuilder {
    public HashCodeBuilder() {

    }

    private int result = 17;

    public HashCodeBuilder append(boolean field) {
        result = 37 * result + (field ? 1 : 0);
        return this;
    }

    public HashCodeBuilder append(byte field) {
        result = 37 * result + (int) field;
        return this;
    }

    public HashCodeBuilder append(char field) {
        result = 37 * result + (int) field;
        return this;
    }

    public HashCodeBuilder append(short field) {
        result = 37 * result + (int) field;
        return this;
    }

    public HashCodeBuilder append(int field) {
        result = 37 * result + field;
        return this;
    }

    public HashCodeBuilder append(long field) {
        result = 37 * result + (int) (field ^ (field >>> 32));
        return this;
    }

    public HashCodeBuilder append(float field) {
        result = 37 * result + Float.floatToIntBits(field);
        return this;
    }

    public HashCodeBuilder append(double field) {
        append(Double.doubleToLongBits(field));
        return this;
    }

    public HashCodeBuilder append(Object field) {
        if(field == null)
            result = 0;
        else if (field.getClass().isArray()) {
            for (int i = Array.getLength(field) - 1; i >= 0; i--) {
                append(Array.get(field, i));
            }
        } else
            append(field.hashCode());
        return this;
    }

    public int toHashCode() {
        return result;
    }

    @Override
    public int hashCode() {
        return result;
    }

    @Override
    public String toString() {
        return String.valueOf(result);
    }

}

测试代码

java 代码

public class MyBean {
    Long id;
    String name;
    char[] chars;
    public MyBean(Long id, String name, char[] chars) {
        super();
        this.id = id;
        this.name = name;
        this.chars = chars;
    }

    @Override
    public int hashCode() {
        return new HashCodeBuilder().append(id)
                    .append(name).append(chars).hashCode();
    }

    public static void main(String[] args) {
        MyBean bean1 = new MyBean(Long.valueOf(10),
                "名称",new char[]{'a','b','c','d','e'});
        MyBean bean2 = new MyBean(Long.valueOf(10),
                "名称",new char[]{'a','b','c','d','e'});
        System.out.println("bean1.hashCode="+bean1.hashCode());
        System.out.println("bean2.hashCode="+bean2.hashCode());
    }
}

评论

2 楼 jasongreen 2007-03-15  

我没有用过common-lang，不是太清楚，我最近在写crazyPOJO的项目，通过Annotation标志value field，然后根据value field生成hashCode，生成equals，生成clone，生成toString，生成toXML，生成toJSON，进行中，今天已经实现了，hashCode和equals，clone等方法，一会上传，大家试用一下

1 楼 v38 2007-03-14  

<br/>
<strong>jasongreen 写道：</strong><br/>
<div class='quote_div'>jakarta-commons-lang已经实现了HashCodeBuilder类，据闻在Hibernate中出错，所以还是选择了自己实现，编码思想来源于 Effective java 一书。而且0依赖。<br/>
==========================</div>
<div class='quote_div'>jakarta-commons-lang已实现的HashCodeBuilder类的错误没有把我们给折磨死～</div>
<div class='quote_div'><br/>
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</div>