[Java] HashMap簡易使用方法及如何排序

宣告：前面KeyType, 後面ValueType

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1 2	HashMap<String, Integer> hashMap = new HashMap<String, Integer>();

放入新元素

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1	hashMap.put(Key,Value);

得到特定Key的Value：若無此Key回傳null

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1	hashMap.get(Key);

更新特定Key,Value：以加一為例

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1	hashMap.put(Key, hashMap.get(Key)+1);

輸出

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for(KetType Key: hashMap.keySet()){     System.out.println(Key, hashMap.get(Key)); }

排序後輸出（以降冪為例)：利用ArrayList

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List<map.entry<String, Integer>> list = new ArrayList<map.entry<string,integer>>(hashMap.entrySet());         Collections.sort(list,new Comparator<map.entry<String, Integer>>() {             @Override             public int compare(Map.Entry<String, Integer> entry1, Map.Entry<String, Integer> entry2) {                 return (entry2.getValue()-entry1.getValue());             }         });         for (Map.Entry<String, Integer> entry:list){             System.out.println(entry.getKey()+" : "+hashMap.get(entry.getKey()));         }