Java遍历Map键、值。获取Map大小的方法

import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class HashMapTest2
{
 public static void main(String[] args)
 {
  HashMap map = new HashMap();
  
  map.put("a","aaaa");
  map.put("b","bbbb");
  map.put("c","cccc");
  map.put("d","dddd");
  
  Set set = map.keySet();
  
  for(Iterator iter = set.iterator(); iter.hasNext();)
  {
   String key = (String)iter.next();
   String value = (String)map.get(key);
   System.out.println(key+"===="+value);
  }
 }
}

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
public class HashMapTest4
{
 public static void main(String[] args)
 {
  HashMap map = new HashMap();
  
  map.put("a","aa");
  map.put("b","bb");
  map.put("c","cc");
  map.put("d","dd");
  
  Set set = map.entrySet();
  
  for(Iterator iter = set.iterator(); iter.hasNext();)
  {
   Map.Entry entry = (Map.Entry)iter.next();
   
   String key = (String)entry.getKey();
   String value = (String)entry.getValue();
   System.out.println(key +" :" + value);
  }
 }
}

public static void main(String[] args) {

    Map map = new HashMap();

    map.put("apple", "新鲜的苹果");     //向列表中添加数据

    map.put("computer", "配置优良的计算机");   //向列表中添加数据

    map.put("book", "堆积成山的图书");     //向列表中添加数据

    System.out.println("Map集合大小为："+map.size());

}