HashMap的三种遍历方法

一下代码分别：

1、用keyset（）和get（）方法实现遍历

2、用entrySet()方法实现遍历

3、用values（）方法实现遍历

 

 

import com.sun.jndi.ldap.Connection;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/*
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/**
 *
 * @author Administrator
 */
public class StuMapTest {
    public static void main(String[] args){

        Map<String,Student> map = new HashMap<String, Student>();
        Student s1 = new Student("宋江", "1001", 33);
        Student s2 = new Student("李逵", "1003", 36);
        Student s3 = new Student("公孙胜", "1004", 39);
        Student c = map.put("1001", s1);
        System.out.println(c);
        map.put("1004", s3);
        map.put("1003", s2);

        //用keyset（）和get（）方法实现遍历
        Set<String> s = map.keySet();
        for(Iterator<String> it=s.iterator();it.hasNext();){
            System.out.println(map.get(it.next()));
        }

        //用entrySet()方法实现遍历
        /*Set<Map.Entry<String,Student>> e=map.entrySet();
        for(Iterator<Entry<String, Student>> it=e.iterator();it.hasNext();){
            System.out.println(it.next());
        }*/

        //用values（）方法实现遍历
       /*Collection<Student> s = map.values();
        for(Iterator<Student> it =s.iterator();it.hasNext();){
            System.out.println(it.next());
        }*/
    }
}

class Student{
    String name;
    String id;
    int age;

    public Student(String name, String id, int age) {
        this.name = name;
        this.id = id;
        this.age = age;
    }

    public String toString(){
        return new StringBuilder().append("id:")
                .append(this.id).append("name:").append(this.name)
                .append("age:").append(this.age).toString();
    }
}