HashMap集合的三种迭代方法

import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

/**
 *
 * @author Administrator
 */
public class StuMapTest {

    public static void main(String[] args) {
        Map<String, Student> map = new HashMap<String, Student>();
        Student s1 = new Student("001", "吕布", 30);
        Student s2 = new Student("002", "赵云", 25);
        Student s3 = new Student("003", "典韦", 33);

 

        map.put("1", s1);
        map.put("2", s2);
        map.put("3", s3);

 

        byValues(map);
        keySet(map);
        entrySet(map);

    }

　　//entrySet方法遍历

    private static void entrySet(Map<String, Student> map){
       Set<Map.Entry<String,Student>> set = map.entrySet();
        for (Iterator<Map.Entry<String, Student>> i = set.iterator(); i.hasNext();) {
            System.out.println(i.next().getValue());

        }

    }

　 //keySet方法遍历

    private static void keySet(Map<String, Student> map){
        Set<String> set = map.keySet();
       
        for (Iterator<String> i = set.iterator(); i.hasNext();) {
            System.out.println(map.get(i.next()));
           
        }
    }

　　//values方法遍历

    private static void byValues(Map<String, Student> map) {

        Collection c = map.values();
        for (Iterator<Student> i = c.iterator(); i.hasNext();) {
            System.out.println(i.next());

        }
    }
}

//定义一个student类

class Student {

    private String id;
    private String name;
    private int age;

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

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