使用TreeSet实现定制排序
我们知道: 一、TreeSet类不但实现了Set的接口,而且还实现了所谓的的java.util.SortedSet接口,所以呢在遍历集合时会进行默认的排序,即升序排列。 eg1(Integer):
package Set类;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;
//创建一个(默认的升序)UnTreeSetTest类...
public class UnTreeSetTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeSet achievements =new TreeSet();
//向该集合中添加元素...啦啦啦
achievements.add(-8);
achievements.add(5);
achievements.add(0);
achievements.add(-3);
achievements.add(6);
//创建Iterator迭代器...啦啦啦
Iterator superiter = achievements.iterator();
//遍历得到集合元素》...嘻嘻嘻
while(superiter.hasNext()) {//这个应该都知道吧...哈哈哈
System.out.println(superiter.next());
}
}
}
运行结果:![在这里插入图片描述](https://img-blog.csdnimg.cn/20200213230924577.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L0NTVV9oamg=,size_16,color_FFFFFF,t_70)
package Set类;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;
//创建一个(默认的升序)UnTreeSetTest类...
public class UnTreeSetTest {
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeSet achievements =new TreeSet();
//向该集合中添加元素...啦啦啦
achievements.add('h');
achievements.add('d');
achievements.add('r');
achievements.add('k');
achievements.add('t');
//创建Iterator迭代器...啦啦啦
Iterator superiter = achievements.iterator();
//遍历得到集合元素》...嘻嘻嘻
while(superiter.hasNext()) {//这个应该都知道吧...哈哈哈
System.out.println(superiter.next());
}
}
}
运行结果: 以上就是默认升序; 二、那如何使用使用TreeSet实现降序排序呢?我们需要使用Comparator接口 eg3(Integer):
package Set类;
import java.util.TreeSet;
import java.util.Comparator;
public class OrderTreeSet {
public static void main(String[] args) {
// TODO Auto-generated method stub
Integer sequence1 = new Integer(9);
Integer sequence2 = new Integer(-3);
Integer sequence3 = new Integer(0);
Integer sequence4 = new Integer(3);
Integer sequence5 = new Integer(-2);
TreeSettreeSet = new TreeSet(new Comparator() {
public int compare(Integer o1, Integer o2) {
return -(o1-o2);
}
});
treeSet.add(sequence1);
treeSet.add(sequence2);
treeSet.add(sequence3);
treeSet.add(sequence4);
treeSet.add(sequence5);
System.out.println(treeSet);
}
}
运行结果: eg4(Character):
package Set类;
import java.util.TreeSet;
import java.util.Comparator;
public class OrderTreeSet {
public static void main(String[] args) {
// TODO Auto-generated method stub
Character sequence1 = new Character('h');
Character sequence2 = new Character('o');
Character sequence3 = new Character('g');
Character sequence4 = new Character('v');
Character sequence5 = new Character('a');
TreeSettreeSet = new TreeSet(new Comparator() {
public int compare(Character o1, Character o2) {
return -(o1-o2);
}
});
treeSet.add(sequence1);
treeSet.add(sequence2);
treeSet.add(sequence3);
treeSet.add(sequence4);
treeSet.add(sequence5);
System.out.println(treeSet);
}
}
运行结果: 以上就是关于TreeSet定制排序(降序)的相关问题了,希望对大家有帮助。
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