Java实现Map遍历key-value的四种方法

        HashMap hashMap = new HashMap();
        hashMap.put("三国演义","罗贯中");
        hashMap.put("水浒传","施耐庵");
        hashMap.put("西游记","吴承恩");
        hashMap.put("红楼梦","曹雪芹");

        /*1、先用keySet()取出所有key值，再取出对应value——增强for循环遍历*/
        System.out.println("====1、先用keySet()取出所有key值，再取出对应value——增强for循环遍历====");
        Set keyset = hashMap.keySet();
        for(Object key:keyset){
            System.out.println(key+"-"+hashMap.get(key));
        }

        /*2、先用keySet()取出所有key值，再取出对应value——使用迭代器遍历*/
        System.out.println("====2、先用keySet()取出所有key值，再取出对应value——使用迭代器遍历====");
        Iterator iterator = keyset.iterator();
        while(iterator.hasNext()){
            Object key = iterator.next();
            System.out.println(key+"-"+hashMap.get(key));
        }

        /*3、通过entrySet()获得key-value值——增强for循环遍历*/
        System.out.println("====3、通过entrySet()获得key-value值——增强for循环遍历====");
        Set set = hashMap.entrySet();
        for(Object key:set){
            Map.Entry entry = (Map.Entry) key;
            System.out.println(entry.getKey()+"-"+entry.getValue());
        }

        /*4、通过entrySet()获得key-value值——使用迭代器遍历*/
        System.out.println("====4、通过entrySet()获得key-value值——使用迭代器遍历====");
        Set set1 = hashMap.entrySet();
        Iterator iterator1 = set1.iterator();
        while(iterator1.hasNext()){
            Object itset = iterator1.next();
            Map.Entry entry = (Map.Entry) itset;
            System.out.println(entry.getKey()+"-"+entry.getValue());
        }

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class MapTraverse {
   	public static void main(String[] args){
        HashMap hashMap = new HashMap();
        hashMap.put("三国演义","罗贯中");
        hashMap.put("水浒传","施耐庵");
        hashMap.put("西游记","吴承恩");
        hashMap.put("红楼梦","曹雪芹");
        /*1、先用keySet()取出所有key值，再取出对应value——增强for循环遍历*/
        System.out.println("====1、先用keySet()取出所有key值，再取出对应value——增强for循环遍历====");
        Set keyset = hashMap.keySet();
        for(Object key:keyset){
            System.out.println(key+"-"+hashMap.get(key));
        }
        /*2、先用keySet()取出所有key值，再取出对应value——使用迭代器遍历*/
        System.out.println("====2、先用keySet()取出所有key值，再取出对应value——使用迭代器遍历====");
        Iterator iterator = keyset.iterator();
        while(iterator.hasNext()){
            Object key = iterator.next();
            System.out.println(key+"-"+hashMap.get(key));
        }
        /*3、通过entrySet()获得key-value值——增强for循环遍历*/
        System.out.println("====3、通过entrySet()获得key-value值——增强for循环遍历====");
        Set set = hashMap.entrySet();
        for(Object key:set){
            Map.Entry entry = (Map.Entry) key;
            System.out.println(entry.getKey()+"-"+entry.getValue());
        }
        /*4、通过entrySet()获得key-value值——使用迭代器遍历*/
        System.out.println("====4、通过entrySet()获得key-value值——使用迭代器遍历====");
        Set set1 = hashMap.entrySet();
        Iterator iterator1 = set1.iterator();
        while(iterator1.hasNext()){
            Object itset = iterator1.next();
            Map.Entry entry = (Map.Entry) itset;
            System.out.println(entry.getKey()+"-"+entry.getValue());
        }
    }
}

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

/*使用HashMap添加3个员工对象，要求
键:员工id
值:员工对象
并遍历显示工资>18000的员工(遍历方式最少两种)员工类:姓名、工资、员工id
*/
public class MapExercise {
    public static void main(String[] args) {
        HashMap hashMap = new HashMap();
        hashMap.put(1, new employee("Tom", 20000.0, 1));
        hashMap.put(2, new employee("Jack", 10000.0, 2));
        hashMap.put(3, new employee("Bob", 30000.0, 3));
        hashMap.put(4, new employee("Marry", 17000.0, 4));
        /*1、通过keySet()获取所有key值，再得到对应的value值——增强for循环遍历*/
        System.out.println("====1、通过keySet()获取所有key值，再得到对应的value值——增强for循环遍历");
        Set keyset = hashMap.keySet();
        for (Object key : keyset) {
            employee m = (employee) hashMap.get(key);
            if (m.getSalary() > 18000) {
                System.out.println(m);
            }
        }
        /*2、通过entrySet()获取key-value值——使用迭代器遍历*/
        System.out.println("====2、通过entrySet()获取key-value值——使用迭代器遍历====");
        Set set = hashMap.entrySet();
        Iterator iterator = set.iterator();
        while (iterator.hasNext()) {
            Object itset = iterator.next();
            Map.Entry entry = (Map.Entry) itset;
            employee m = (employee) entry.getValue();
            if (m.getSalary() > 18000) {
                System.out.println(m);
            }
        }

    }
}
class employee{
    private String name;
    private Double salary;
    private int id;

    public employee(String name, Double salary, int id) {
        this.name = name;
        this.salary = salary;
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Double getSalary() {
        return salary;
    }

    public void setSalary(Double salary) {
        this.salary = salary;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    @Override
    public String toString() {
        return "employee{" +
                "name='" + name + '\'' +
                ", salary=" + salary +
                ", id=" + id +
                '}';
    }
}