java 键值对 Map<String, String>

import java.util.Map;
import java.util.Map.Entry;

//声明键值对对象

Map<String, String> params=new HashMap<String, String> ();

params.put("A", "1");

params.put("B", "2");

String postdata="";
//获取键和值
for(Entry<String,String> entry:params.entrySet()) 
postdata+= entry.getKey()+"="+entry.getValue()+"&";