Java hashmap 不能判断重复键值的问题

Question

想让String[]数组存入到一个map中，但是不能判断出已经存在的相同元素

lists中的内容如下:

最后wordsCount中包含有3个相同的(i,will)：1的key-value值？

怎样使结果为(i,will):3
新手求助

Answer 1

把String数组换成一个类吧，拥有两个String属性的类，经测试可以实现，希望对你有帮助。另外可以查看一下对equals和hashcode重写的写法

public class OverHashcode {
static Map wordsCount = new HashMap<>();
static List list = new ArrayList();

public static void toMap() {
    for (LikeStringArray tempStr : list) {
        if (wordsCount.containsKey(tempStr)) {
            wordsCount.put(tempStr, wordsCount.get(tempStr) + 1);
        } else {
            wordsCount.put(tempStr, 1);
        }
    }

    for (Map.Entry<LikeStringArray, Integer> entry : wordsCount.entrySet())
        System.out.printf("%s:%d\n",  entry.getKey(), entry.getValue());
}
public static void main(String[] args) {
    list.add(new LikeStringArray("i","do"));
    list.add(new LikeStringArray("i","do"));
    list.add(new LikeStringArray("i","will"));
    list.add(new LikeStringArray("i","will"));
    list.add(new LikeStringArray("i","will"));
    list.add(new LikeStringArray("i","am"));
    toMap();

}

}

class LikeStringArray{
String id;
String name;
LikeStringArray(String id,String name){
this.id= id;
this.name = name;
}
@Override
public int hashCode() {
//返回的hash值进行比较，若equals方法返回true则hashCode方法也应该返回true
return this.name.hashCode()+this.id.hashCode();
}
@Override
public boolean equals(Object obj) {
LikeStringArray other = (LikeStringArray) obj;
//id和name都相同就返回true即是内容上的比较
if(id.equals(other.id)&&name.equals(other.name)){
return true;
}
return super.equals(obj);
}
//输出时别忘了重写toString方法
public String toString() {

    return "<"+id+","+name+">";
}

}