Java数据结构的一个小题目，有人能解决下吗

[yaojiayang123]

4.写一个Student类, 包含属性id[1-30), grade[1-6], score[0-100], 所有属性都是随机生成
创建一个Set集合, 保存20个对象, 如果两个对象的id是一样的,则不允许添加.
使用迭代器遍历集合,打印输出对象的信息, 并找出分数最高的同学和分数最低的同学, 最后打印输出最高分和最低分同学信息。


代码敬上，我想问我运行时每次遍历到第七个学生的score都读不出来，这是为什么？？？？ 有人能解决一下吗，感谢。

Java code
?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
package cn.yann.exp4;

import java.util.HashSet;
import java.util.Set;
import java.util.Iterator;

package cn.yann.exp4;
 
public class Student {
    private int id;
    private int grade;
    private int score;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public int getGrade() {
        return grade;
    }
    public void setGrade(int grade) {
        this.grade = grade;
    }
    public int getScore() {
        return score;
    }
    public void setScore(int score) {
        this.score = score;
    }
    public Student(){
        id = (int)(Math.random()*28) + 1;
        grade = (int)(Math.random()*5) + 1;
        score = (int)(Math.random()*100);
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + id;
        return result;
    }
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Student other = (Student) obj;
        if (id != other.id)
            return false;
        return true;
    }
     
     
}

public class Test {

public static void main(String[] args) {
Set<Student> s = new HashSet<Student>();
int i = 1;
while( i <= 20){
Student stu = new Student();
if(s.contains(stu)){
System.out.println("id相同,添加失败");
System.out.println(stu.getId());
}
else{
s.add(stu);
System.out.println("添加学生"+i+"成功:"+stu.getId());
i++;
}	
}

Iterator<Student> it = s.iterator();
i = 1;
while(it.hasNext()){
System.out.print("学生"+i+"id:"+it.next().getId()+"  ");
System.out.print("grade:"+it.next().getId()+"  ");
System.out.print("score:"+it.next().getId());
System.out.println();
i++;
}



}

}

[BUBU_CH]

最后打印的地方改一下 每次调用next的时候都会让迭代器指向下一个的

while (it.hasNext()) {
			Student tempStu = it.next();
			System.out.println("学生" + i + "id:" + tempStu.getId() + " grade:" + tempStu.getGrade() + "  score:" + tempStu.getScore());
			i++;
		}

[rickylin86]

最后显示那里每次while循环都调用了三次it.next().所以自然会20/3=7,所以到了第七个的时候就出现问题了.

[乌鲁基欧拉]

it.next()没调用一次 指针都要指向下一个 所以用个东西接收下it.next()就可以了

[sz_modai]

这是你想实现的代码，在创建randomId时，*30+1满足30个学生，并且在迭代器部分多次使用了it.next();导致超出了迭代器循环的范围 public class Student { private int id; private int grade; private int score; public int getId() { return id; } public void setId(int id) { this.id = id; } public int getGrade() { return grade; } public void setGrade(int grade) { this.grade = grade; } public int getScore() { return score; } public void setScore(int score) { this.score = score; } @Override public int hashCode() { final int prime = 31; int result = 1; result = prime * result + grade; result = prime * result + id; result = prime * result + score; return result; } @Override public boolean equals(Object obj) { if (this == obj) return true; if (obj == null) return false; if (getClass() != obj.getClass()) return false; Student other = (Student) obj; if (grade != other.grade) return false; if (id != other.id) return false; if (score != other.score) return false; return true; } public Student(){ id = (int)(Math.random()*30) + 1; grade = (int)(Math.random()*5) + 1; score = (int)(Math.random()*100)+1; } } public class Test { public static void main(String[] args) { Set<Student> s = new HashSet<Student>(); int i = 1; while( i <= 30){ Student stu = new Student(); if(s.contains(stu)){ System.out.println("id相同,添加失败"); System.out.println(stu.getId()); } else{ s.add(stu); System.out.println("添加学生"+i+"成功:"+stu.getId()); i++; } } Iterator<Student> it = s.iterator(); int j = 1; do{ Student stu = it.next(); System.out.print("学生"+j+"id:"+stu.getId()+" "); System.out.print("grade:"+stu.getGrade()+" "); System.out.print("score:"+stu.getScore()); System.out.println(); j++; }while(it.hasNext()); } }

[lu的博客]