问题描述
importjava.util.Map;importjava.util.HashMap;importjava.util.Set;importjava.util.HashSet;importjava.util.Iterator;importjava.util.Hashtable;importjava.util.TreeMap;classHashMaps{publicstaticvoidmain(String[]args){Mapmap=newHashMap();map.put("a","aaa");map.put("b","bbb");map.put("c","ccc");map.put("d","ddd");map.put("e","eee");//System.out.println(map.size());//publicintsize()返回此映射中的键-值映射关系数。System.out.println(map.get("e"));//get()方法的参数是key类型,是根据key值来决定结果输出eeeSetkey1=map.keySet();Setkey2=map.keySet();Setkey3=map.keySet();System.out.println(key1);System.out.println(key2);System.out.println(key3);/*这段代码输出[d,a,c,b,e][d,a,c,b,e][d,a,c,b,e]*/Iteratoriterator=map.keySet().iterator();while(iterator.hasNext()){Objectkey=iterator.next();System.out.println(key);System.out.println("map.get(key)is:"+map.get(key));}}}为什么会出现这种错误啊一开始调试的时候还行的啊在没加入System.out.println(map.size());这句话之前还行的啊加入之后将他注释也不行我用的是jcreator--------------------Configuration:<Default>--------------------Usage:java[-options]class[args...](toexecuteaclass)orjava[-options]-jarjarfile[args...](toexecuteajarfile)whereoptionsinclude:-clienttoselectthe"client"VM-servertoselectthe"server"VM-hotspotisasynonymforthe"client"VM[deprecated]ThedefaultVMisclient.-cp<classsearchpathofdirectoriesandzip/jarfiles>-classpath<classsearchpathofdirectoriesandzip/jarfiles>A;separatedlistofdirectories,JARarchives,andZIParchivestosearchforclassfiles.-D<name>=<value>setasystemproperty-verbose[:class|gc|jni]enableverboseoutput-versionprintproductversionandexit-version:<value>requirethespecifiedversiontorun-showversionprintproductversionandcontinue-jre-restrict-search|-jre-no-restrict-searchinclude/excludeuserprivateJREsintheversionsearch-?-helpprintthishelpmessage-Xprinthelponnon-standardoptions-ea[:<packagename>...|:<classname>]-enableassertions[:<packagename>...|:<classname>]enableassertions-da[:<packagename>...|:<classname>]-disableassertions[:<packagename>...|:<classname>]disableassertions-esa|-enablesystemassertionsenablesystemassertions-dsa|-disablesystemassertionsdisablesystemassertionsProcesscompleted.
解决方案
解决方案二：
map.keySet().size()
解决方案三：
你的程序在我机器上运行好着了，System.out.println(map.size());//publicintsize()返回此映射中的键-值映射关系数。输出为5我的系统为jdk6
解决方案四：
楼主：程序没错啊……运行可以得到结果啊不加keySet()也可以
解决方案五：
顶
解决方案六：
能运行！！！jdk1.5
解决方案七：
现在还有人用JCreator?跟Eclipse比起来有什么优势吗？