哈希表-java

import java.util.HashMap;
import java.util.Iterator;

public class JavaHashMap {

  public static void main(String[] args) {

  //定义HashMap
  HashMap<String, String> hm = new HashMap<String, String>();
  //添加字典
  hm.put("username", "password");
  hm.put("Jim", "1155689");
  hm.put("Jane", "1255669");
  hm.put("Kevin", "1165669");

  //测试 key 是否包含 username,返回值为 true/false
  System.out.println(hm.containsKey("username"));
  System.out.println("===================>");

  //获取 key 所对应的 vlaue
  System.out.println(hm.get("Jim"));
  System.out.println("===================>");

  //获取整个字典数据
  System.out.println(hm.entrySet());
  System.out.println("===================>");

  //循环打印每一对 key:value
  Iterator<?> it = hm.entrySet().iterator();
  while (it.hasNext()) {
  System.out.println(it.next());
  }
  System.out.println("===================>");

  //分别获取 key 的值， 和 value 的值。
  Iterator<String> it2 = hm.keySet().iterator();
  while (it2.hasNext()) {
  //获得字典的 key(username)
  String username = (String) it2.next();
  System.out.println(username);
  //获得字典的 value(节点)
  String password = hm.get(username);
  System.out.println(password);
  }
  }
}