javaå°listç¸å次æ°è¾åºå°å¦å¤ä¸ä¸ªlistï¼å¯ä»¥ä½¿ç¨mapä½ä¸ºä¸é´è½¬æ¢çç»åï¼å°éå¤ç次æ°èµå¼ç»valueï¼èkeyå¼ä¸ºliståæ¥çå
容ï¼å®ä¾å¦ä¸ï¼import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class Test {public static void main(String[] args) {List list = new ArrayList();//æ°å»ºä¸ä¸ªéålist.add(1);list.add(2);list.add(2);list.add(5);list.add(4);list.add(4);list.add(3);list.add(2);Map map = new HashMap();//æ°å»ºä¸ä¸ªmapéåï¼ç¨æ¥ä¿åéå¤ç次æ°for(Integer obj: list){if(map.containsKey(obj)){//å¤ææ¯å¦å·²ç»æ该æ°å¼ï¼å¦æï¼åå°æ¬¡æ°å 1map.put(obj, map.get(obj).intValue() + 1);}else{map.put(obj, 1);}}ArrayList newList = new ArrayList(map.values());//æ°å»ºå¦å¤ä¸ä¸ªlistSystem.out.println(newList.toString());}}
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