Java中两个Map的加减

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package com.map;import java.util.Iterator;import java.util.Map;import java.util.HashMap;import java.util.Set;public class AddMap {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stub        Map<String,Double> AMap = new HashMap<String,Double>(){{        put("A",1.0);        put("B",2.0);        put("C",-3.0);        }};                Map<String,Double> BMap = new HashMap<String,Double>(){{        put("B",-2.0);        put("C",3.0);        put("D",6.0);        }};                 Map<String,Double> CMap = addWeight(AMap,BMap);                for(String s : CMap.keySet())        {        System.out.println(s + " = " + CMap.get(s));        }        }public static Map<String,Double> addWeight(Map<String,Double> goldMap,Map<String,Double> preMap){ Map<String,Double> addMap = new HashMap<String,Double>();      for(String s : preMap.keySet())     {     if(goldMap.containsKey(s))     {          addMap.put(s, (goldMap.get(s) + preMap.get(s)));          } else     {         addMap.put(s, preMap.get(s));     }     }     for(String str : goldMap.keySet())     {     if(!preMap.containsKey(str))     {    addMap.put(str, goldMap.get(str));      }     }          //删除值为空的项     //集合类的都不能在循环的时候删除，因为删除元素后集合发生改变继而不能循环了     //这种删除方式以后不要再用了,严重出错     /*for(String key : cutMap.keySet())      {     Double value = cutMap.get(key);     if(value == 0.0)     {     cutMap.remove(key);     }     }*/         Set mapset = addMap.entrySet();        Iterator iterator = mapset.iterator();                while(iterator.hasNext())        {            Map.Entry mapEntry = (Map.Entry)iterator.next();             Double value =(Double)mapEntry.getValue();                        if(value == 0.0)            {            iterator.remove();            }         }          return addMap;}/** * 两个Map相减 * @param goldMap * @param preMap * @return */public static Map<String,Double> cutWeight(Map<String,Double> goldMap,Map<String,Double> preMap){ Map<String,Double> cutMap = new HashMap<String,Double>();     for(String s : preMap.keySet())     {     if(goldMap.containsKey(s))     {          cutMap.put(s, (goldMap.get(s)-preMap.get(s)));          } else     {         cutMap.put(s, -(preMap.get(s)));     }     }     for(String str : goldMap.keySet())     {     if(!preMap.containsKey(str))     {    cutMap.put(str, goldMap.get(str));      }     }        //删除值为空的项                 Iterator iterator = cutMap.entrySet().iterator();                while(iterator.hasNext())        {            Map.Entry mapEntry = (Map.Entry)iterator.next();             Double value =(Double)mapEntry.getValue();                        if(value == 0.0)            {            iterator.remove();            }         }          return cutMap;}}
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