编写程序将一组学生对象的姓名和成绩存入到一个树集（TreeSet）中，完成以下要求：

•    使得按照成绩自动降序排列，并输出排序的结果。

•    从一个无序数组中，剔除重复元素，并按升序排序。

import java.util.TreeSet;
import java.util.*;
public class S6_5 {public static void main(String [] args){TreeSet ts=new TreeSet(new Comparator() {@Overridepublic int compare(Object o1, Object o2) {Student s1=(Student)o1;Student s2=(Student)o2;if(s1.score.hashCode()>(s2.score.hashCode())){return -1;}else if(s1.score.hashCode()<s2.score.hashCode()){return 1;}else {return s1.name.compareTo(s2.name);//当score相等时，比较name;}}});ts.add(new Student("98","zhang"));ts.add(new Student("60","li"));ts.add(new Student("60","ab"));System.out.println(ts);TreeSet st=new TreeSet();st.add(123);st.add(12);st.add(12);st.add(34);st.add(356);System.out.println(st);}
}
class Student {public  String score;public  String name;public Student(String score,String name){this.score=score;this.name=name;}public String toString() {return score + ":" + name;}public int hashCode(){return score.hashCode();}
}

运行结果：

5.

import java.util.*;
public class S6_6
{public static void main(String[] args){Scanner reader=new Scanner(System.in);HashMap<Integer,Integer> tm=new HashMap<Integer,Integer>();while (true){int a=reader.nextInt();if (a==0){break;}if (tm.containsKey(a)){int value1=tm.get(a);value1++;tm.put(a,value1);}else{tm.put(a,1);}}Collection<Integer> c = tm.values();Object[] obj = c.toArray();Arrays.sort(obj);//升序排列Set keySet=tm.keySet();Iterator it2=keySet.iterator();while (it2.hasNext()){Object key=it2.next();Object value=tm.get(key);if (obj[tm.size()-1]==value){System.out.println("频率最高的数据为：");System.out.println(key);}//System.out.println(key+":"+value);}}
}

运行结果：

import java.util.*;
public class S6_8 {public static void main(String[] args) {String str = "Today, We have a class of java, as we kown, java is an object oriented  programming language, and java is fun! wish you enjoy it";HashMap<String, Integer> hm = new HashMap<>();    //定义一个双列集合String[] strs = str.split("[ \\n\\t\\r.,;:!?()]");                                               //分割成若干字符串for (int i = 0; i < strs.length; i++) {                                  //判断每个字符串，是存在于集合里if (!hm.containsKey(strs[i])) {hm.put(strs[i], 1);                    //如果不存在，则存进去} else {Integer counts = hm.get(strs[i]);                        //如果存在 ，先找到 此key对应的 value值hm.put(strs[i], counts + 1);                   //覆盖前者的的key值，并且比前者多加一次}}Iterator<String> it=hm.keySet().iterator();                    //获取HashMap所有的key集合并遍历while(it.hasNext()) {String keyName=it.next();System.out.println(keyName+"->"+hm.get(keyName));}}
}