TreeSet的定制排序

╰+攻爆jí腚メ 2022-09-27 04:51 179阅读 0赞

# 方式1：在元素自身中定义排序规则 #

需要元素自身实现Comparable接口

/*** *TreeSet是一个有序集合，TreeSet中元素将按照升序排列，缺省是按照 自然顺序进行排列，意味着TreeSet中元素要实现Comparable接口。 我们可以在构造TreeSet对象时，传递实现了Comparator接口的比较器对象。 注意排序時：當主要的條件相同時，判斷次要條件。 * @author Administrator * */
    public class TreeSetTest { 
         public static void main(String[] args) {
              TreeSet treeset = new TreeSet();//定义一个集合
              treeset.add(new person2(10, "liuyia"));
              treeset.add(new person2(10, "liuyib"));
              treeset.add(new person2(15, "liuyi34"));
              treeset.add(new person2(11, "liuyi4"));
              treeset.add(new person2(12, "liuyi4"));
    
              Iterator itera = treeset.iterator();
              while (itera.hasNext()) {
               System.out.println(itera.next());
              }
    
         }
    }
    
    class person2 implements Comparable {
       //实现Comparable 接口 private int age;
    
         private String name;
    
         public int getAge() {
          return age;
         }
    
         public void setAge(int age) {
          this.age = age;
         }
    
         public String getName() {
          return name;
         }
    
         public void setName(String name) {
          this.name = name;
         }
    
         public person2(int age, String name) {
          this.age = age;
          this.name = name;
    
    
    
         }
    
    
         public int compareTo(Object o) {
              if(!(o instanceof person2)) throw new RuntimeException("对象类型不一致!");
                   person2 p = (person2)o;
                   if(this.age>p.age){
                    return -1;
                   }
                   if(this.age<p.age){
                    return 1;
                   }
    
                   if(this.age==p.age){ 
                    return this.name.compareTo(p.name);//當主要的條件也就是age的值相同時時候此時判斷次要條件姓名
                   }        
              return -1;
    
         }
         //打印结果
         public String toString(){
          return age+" = "+"name"+name;
         }
    }

# 方式2（传给集合一个自定义排序器） #

写个实现Comparble接口的排序器

public class TreeSetTest {
         public static void main(String[] args) {
             //定义一个集合,并将自定义的排序器传给集合。这样该集合就会使用我们定义的排序规则来排序
              TreeSet treeset = new TreeSet( new mycomp());
              treeset.add(new person2(10, "liuyia"));
              treeset.add(new person2(10, "liuyib"));
              treeset.add(new person2(15, "liuyi34"));
              treeset.add(new person2(11, "liuyi4"));
              treeset.add(new person2(12, "liuyi4"));
    
              Iterator itera = treeset.iterator();
              while (itera.hasNext()) {
               System.out.println(itera.next());
              } 
         }
    }
    
    class person2 {
         private int age;   
         private String name;
    
         public int getAge() {
              return age;
         }
    
         public void setAge(int age) {
              this.age = age;
         }
    
         public String getName() {
              return name;
         }
    
         public void setName(String name) {
              this.name = name;
         }
    
         public person2(int age, String name) {
              this.age = age;
              this.name = name;
         }
         public String toString(){
              return age+" = "+"name"+name;
         }
    }
    
    
    class mycomp implements Comparator{
    
         public int compare(Object o1, Object o2) {
              person2 p1 = (person2)o1;
              person2 p2 = (person2)o2;
              return -(p1.getAge()- p2.getAge());
         }
    }