map的查询和修改方法

1：map查询的方法

   

package com.cn.util;

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

//循环遍历map的方法
public class Util {
    public static void main(String[] args) {
        Map<String, Integer> tempMap = new HashMap<String, Integer>();
        tempMap.put("a", 1);
        tempMap.put("b", 2);
        tempMap.put("c", 3);
        // JDK1.4中
        // 遍历方法一 hashmap entrySet() 遍历
        System.out.println("方法一");
        Iterator it = tempMap.entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry entry = (Map.Entry) it.next();
            Object key = entry.getKey();
            Object value = entry.getValue();
            System.out.println("key=" + key + " value=" + value);
        }
        System.out.println("");
        // JDK1.5中,应用新特性For-Each循环
        // 遍历方法二
        System.out.println("方法二");
        for (Map.Entry<String, Integer> entry : tempMap.entrySet()) {
            String key = entry.getKey().toString();
            String value = entry.getValue().toString();
            System.out.println("key=" + key + " value=" + value);
        }
        System.out.println("");

        // 遍历方法三 hashmap keySet() 遍历
        System.out.println("方法三");
        for (Iterator i = tempMap.keySet().iterator(); i.hasNext();) {
            Object obj = i.next();
            System.out.println(obj);// 循环输出key
            System.out.println("key=" + obj + " value=" + tempMap.get(obj));
        }
        for (Iterator i = tempMap.values().iterator(); i.hasNext();) {
            Object obj = i.next();
            System.out.println(obj);// 循环输出value
        }
        System.out.println("");

        // 遍历方法四 treemap keySet()遍历
        System.out.println("方法四");
        for (Object o : tempMap.keySet()) {
            System.out.println("key=" + o + " value=" + tempMap.get(o));
        }
        System.out.println("11111");

        // java如何遍历Map <String, ArrayList> map = new HashMap <String,
        // ArrayList>();
        System.out
                .println("java 遍历Map <String, ArrayList> map = new HashMap <String, ArrayList>();");
        Map<String, ArrayList> map = new HashMap<String, ArrayList>();
        Set<String> keys = map.keySet();
        Iterator<String> iterator = keys.iterator();
        while (iterator.hasNext()) {
            String key = iterator.next();
            ArrayList arrayList = map.get(key);
            for (Object o : arrayList) {
                System.out.println(o + "遍历过程");
            }
        }
        System.out.println("2222");
        Map<String, List> mapList = new HashMap<String, List>();
        for (Map.Entry entry : mapList.entrySet()) {
            String key = entry.getKey().toString();
            List<String> values = (List) entry.getValue();
            for (String value : values) {
                System.out.println(key + " --> " + value);
            }
        }
    }
}

2：map的查询方法

    

package com.cn.util;

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

public class MapTest {
    public static void Test1() {
        Map<String, Integer> m = new HashMap<String, Integer>();
        m.put("1", 20);
        m.put("2", 30);
        Set<String> s = m.keySet();// 获取KEY集合
        for (String str : s) {
            m.put(str, (int) (m.get(str) * 1.3));// 往key里面賦值
        }
        System.out.println(m.get("1") + " " + m.get("2"));
    }

    public static void main(String[] args) {
        Test1();
    }
}