zoukankan      html  css  js  c++  java
  • LinkedHashMap,HashMap,TreeMap

    package com.test;
    
    import java.util.*;
    
    /**
     * @author ****
     * @create 2017-07-10 20:28
     */
    public class LinkedHashMapAndHashMap {
    
        public static void main(String[] args) {
            System.out.println("LinkedHashMap测试开始");
            linkedHashMapTest();
            System.out.println("HashMap测试开始");
            hashMapTest();
            System.out.println("TreeMap测试开始");
            treeMapTest();
        }
    
        private static void linkedHashMapTest() {
            Map<Integer, String> linkedHashMap = new LinkedHashMap<Integer, String>();
            linkedHashMap.put(9, "植物");
            linkedHashMap.put(7, "动物");
            linkedHashMap.put(5, "微生物");
            linkedHashMap.put(null,null);
            linkedHashMap.put(null,"null");
            for (Map.Entry<Integer, String> entry : linkedHashMap.entrySet()) {
                System.out.println(entry.getKey() + ":" + entry.getValue());
            }
        }
    
        private static void hashMapTest() {
            Map<Integer, String> hashMap = new HashMap<Integer, String>();
            Collections.synchronizedMap(hashMap);
            hashMap.put(9, "植物");
            hashMap.put(7, "动物");
            hashMap.put(5, "微生物");
            hashMap.put(null,null);
            hashMap.put(null,"null");
            Iterator iterator = hashMap.keySet().iterator();
            while (iterator.hasNext()) {
                Object o = iterator.next();
                System.out.println( o + ":" + hashMap.get(o));
            }
        }
    
        private static void treeMapTest() {
            Map<Integer, String> treeMap = new TreeMap<Integer, String>();
            treeMap.put(9, "植物");
            treeMap.put(7, "动物");
            treeMap.put(5, "微生物");
            for(Iterator iterator = treeMap.keySet().iterator();iterator.hasNext();) {
                Object key = iterator.next();
                System.out.println(key + ":" + treeMap.get(key));
            }
        }
    }

    从Map中按插入数据顺序取数据的时候用LinkedHashMap,HashMap和TreeMap都会默认排序。

  • 相关阅读:
    表单高级和表格高级
    XHTML基础知识
    浅析JavaScript访问对象属性和方法及区别
    互联网盈利模式研习笔记之二:佣金与分成
    互联网盈利模式研习笔记之一:流量变现
    前端两年开发经验需要了解的常识!
    拖拽原理
    js中常见兼容性
    前端性能优化
    JS框架常识。
  • 原文地址:https://www.cnblogs.com/jqlbj/p/7147686.html
Copyright © 2011-2022 走看看