初始化一個map 1 2 3 4 5 Map<String, String> map = new HashMap<String, String>(); map.put("1", "hell"); map.put("2", "hello"); map.put("3", "hel"); map.put( ...
初始化一個map
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Map<String, String> map = new HashMap<String, String>();
map.put("1", "hell");
map.put("2", "hello");
map.put("3", "hel");
map.put("4", "hello");
|
1、第一種方式，普遍使用
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Set<String> keySet = map.keySet();
for (String key : keySet) {
System.out.println("key= " + key + " and value= " + map.get(key));
}
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2、第二種方式，容量大時推薦使用
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Set<Map.Entry<String,String>> entySet = map.entrySet();
for (Map.Entry<String, String> entry : entySet) {
System.out.println("key= " + entry.getKey() + " and value= "
+ entry.getValue());
}
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實驗發現輸出的順序是亂的，排個序吧
1、按照key值排序
首先寫個排序類
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private static class KeyComparator implements
Comparator<Map.Entry<String, String>> {
public int compare(Map.Entry<String, String> m,
Map.Entry<String, String> n) {
return m.getKey().compareTo(n.getKey());
}
}
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把數據放在list裡邊才可以使用
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List<Map.Entry<String, String>> list = new ArrayList<Map.Entry<String, String>>();
list.addAll(map.entrySet());
KeyComparator kc = new KeyComparator();
Collections.sort(list, kc);
for (Iterator<Map.Entry<String, String>> it = list.iterator(); it
.hasNext();) {
System.out.println(it.next());
}
|
2、按照Value值排序
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private static class ValueComparator implements
Comparator<Map.Entry<String, String>> {
public int compare(Map.Entry<String, String> m,
Map.Entry<String, String> n) {
return m.getValue().compareTo(n.getValue());
}
}
|
排序輸出
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list.clear();
list.addAll(map.entrySet());
ValueComparator vc = new ValueComparator();
Collections.sort(list, vc);
for (Iterator<Map.Entry<String, String>> it = list.iterator();
it.hasNext();) {
System.out.println(it.next());
}
|
Tips: 如有錯誤請指出，我會及時修改
