Java 基础一些代码练习笔记( TreeSet 排序)

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import java.util.Comparator;import java.util.Iterator;import java.util.TreeSet;public class TreeSetTest2{public static void main(String[] args){TreeSet set = new TreeSet(new PersonComparator());Person p1 = new Person(10);Person p2 = new Person(20);Person p3 = new Person(30);Person p4 = new Person(40);set.add(p1);set.add(p2);set.add(p3);set.add(p4);for(Iterator iter = set.iterator(); iter.hasNext();){Person p = (Person)iter.next();System.out.println(p.score);}}}class Person{int score;public Person(int score){this.score = score;}public String toString(){return String.valueOf(this.score);}}class PersonComparator implements Comparator{public int compare(Object o1, Object o2){Person p1 = (Person)o1;Person p2 = (Person)o2;return p1.score - p2.score;//倒序//return p2.score - p1.score;}}
import java.util.Comparator;import java.util.Iterator;import java.util.TreeSet;public class TreeSetTest3{public static void main(String[] args){TreeSet  set = new TreeSet(new MyComparator());set.add("C");set.add("A");set.add("B");set.add("E");set.add("F");set.add("D");for(Iterator iter = set.iterator(); iter.hasNext();){String value = (String)iter.next();System.out.println(value);}}}class MyComparator implements Comparator{public int compare(Object o1, Object o2){String s1 = (String)o1;String s2 = (String)o2;return s2.compareTo(s1);}}



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