Java SE 第四十六,七 迭代器,TreeSet及Comparator深度剖析,实现自己的Comparator及Collection详解

1.TreeSet的add()方法:

public class TreeSetTest3

{

public staic void main(String[] args)

{

TreeSet set = new TreeSet();

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 arg0,Object arg1)

{

String s1 = (String)arg0;

String s2 = (String)arg1;

return s2.compareTo(s1);

}

}

2.自定义comparator()方法,实现将自定义类的对象添加到TreeSet对象中.

import java.util.Comparator;
import java.util.Iterator;
import java.util.TreeSet;

public class TreeSetTest2 {
    public static void main(String[] args) {
        Person p1 = new Person(10);
        Person p2 = new Person(20);
        Person p3 = new Person(30);
        Person p4 = new Person(40);
        TreeSet set1 = new TreeSet(new Person());
       
        set1.add(p1);
        set1.add(p2);
        set1.add(p3);
        set1.add(p4);
        for(Iterator iter = set1.iterator();iter.hasNext();){
            System.out.println(iter.next());
        }
           
    }

}
class Person implements Comparator{
    int score;
    public Person(){
       
    };
    public Person(int score) {
        this.score = score;
    }
    public String toString() {
    return String.valueOf(this.score);   
    }
    public int compare(Object arg0, Object arg1) {
        Person p1 = (Person)arg0;
        Person p2 = (Person)arg1;
        if(p1.score>p2.score)
            return 1;
        if(p1.score<p2.score)
            return -1;
        if(p1.score == p2.score)
            return 0;
        return 0;
           
    }
}
3.类Collections是Collection接口的一个实现类其操作对象时集合.

包括static方法: