java-14习题

 1.使用TreeSet集合生成一个不重复随机数组，该数组包含10个100以内的随机整数。输出该随机数组。 


 4 import java.util.Iterator;
 5 import java.util.TreeSet;
 6 
 7 public class Test {
 8     public static void main(String[] args) {
 9         int x;
10         int arr []=new int [20];
11         TreeSet<Integer> set =new TreeSet<Integer>();
12 
13         int d=0;
14         while(d<10){
15             x=(int)(Math.random()*100);
16             if(set.add(x))//TreeSet是去重复的集合，集合中没有的返回true
17                 d++;
18         }
19         /*
20          while(set.size()<10){
21             x=(int)(Math.random()*100);
22            set.add(x);
23         }
24          */
25         int i=1;
26         Iterator<Integer>it=set.iterator();
27         while(it.hasNext()){
28             int t=it.next();
29             arr[i]=t;
30             i++;
31         }
32         for(i=1;i<=10;i++)
33             System.out.print(arr[i]+" ");
34     }
35 }

 2.创建一个Student类，使用比较器Comparator，根据学号进行对象排序。

 
 4 import java.util.Comparator;
 5 import java.util.Iterator;
 6 import java.util.TreeSet;
 7 class Student {
 8     private String name;
 9     private String id;
10     public Student(){    
11     }
12     public Student(String name,String id){
13         this.name=name;
14         this.id=id;
15     }
16     public String getName() {
17         return name;
18     }
19     public String getId() {
20         return id;
21     }
22 }
23 class DescSort implements Comparator<Student> {
24 
25     public int compare(Student s1, Student s2) {
26         if(s1.getId().compareTo(s2.getId())>0)
27             return -1;
28         else if(s1.getId().compareTo(s2.getId())<0)
29             return 1;
30         else return 0;
31     }
32 }
33 public class Test {
34     public static void main(String[] args)   {
35     Comparator<Student> comp=new DescSort();
36     TreeSet<Student> t=new TreeSet<Student>(comp);
37     t.add(new Student("小赵","11517447"));
38     t.add(new Student("小王","11517432"));
39     t.add(new Student("小明","11517413"));
40     t.add(new Student("小红","11517402"));
41     t.add(new Student("小李","11517425"));
42     Iterator<Student>it=t.iterator();
43     while(it.hasNext()){
44         Student stu=it.next();
45         System.out.println(stu.getName()+"的学号是"+stu.getId());
46     }    
47 }
48 }

输出结果：