对LIST类型的集合根据条件进行合并操作

对List类型的集合根据条件进行合并操作

public class Student {
    public static void main(String[] args) {
        List list = new ArrayList();
        list.add(new S("张三 ,数学,0.15"));
        list.add(new S("张三 ,数学,0.35"));
        list.add(new S("张三 ,语文,0.15"));
        list.add(new S("李四 ,语文,0.35"));
        list.add(new S("王五 ,体育,0.15"));
        list.add(new S("王五 ,体育,0.5"));
        Map map = new HashMap();
        for (S s : list) {
            if (map.containsKey(s)) {
                map.put(s, S.merge(s, map.get(s)));
            } else {
                map.put(s, s);
            }
        }
        System.out.println(map.values());
    }
}
 
class S {
    String name;
    String date;
    double num;
 
    S(String name, String date, double num) {
        build(name, date, num);
    }
 
    S(String str) {
        String[] s = str.split(",");
        build(s[0], s[1], Double.parseDouble(s[2]));
    }
 
    private void build(String name, String date, double num) {
        this.name = name;
        this.date = date;
        this.num = num;
    }
 
    static S merge(S s1, S s2) {
        if (!s1.equals(s2)) {
            throw new IllegalArgumentException();
        }
        return new S(s1.name, s1.date, s1.num + s2.num);
    }
 
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((date == null) ? 0 : date.hashCode());
        result = prime * result + ((name == null) ? 0 : name.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;
        S other = (S) obj;
        if (date == null) {
            if (other.date != null)
                return false;
        } else if (!date.equals(other.date))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }
 
    @Override
    public String toString() {
    	return "S [name=" + name + ", date=" + date + ", num=" + num + "]";
	}
}

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