我有一个 HashMap 列表,我想在 Java 中按升序对其进行排序。
我正在使用自定义比较器来实现逻辑,但它失败了。它只是根据映射键对列表进行分组。它没有完全对列表进行排序。
我的代码看起来像-
public class ListMap {
public static void main(String[] args) {
Calendar cal = Calendar.getInstance();
List<HashMap<String, String>> list = new ArrayList<>();
for (int i = 0; i < 20; i++) {
int value = randInt(1, 20);
long timeInMillis = cal.getTimeInMillis();
HashMap<String, String> mp = new HashMap<>();
mp.put("" + value, "Values" + value + ":" + timeInMillis);
list.add(mp);
}
Collections.sort(list, new Comparator<Map<String, String>>() {
@Override
public int compare(Map<String, String> map1,
Map<String, String> map2) {
String val1 = "";
String val2 = "";
for (Map.Entry<String, String> entry : map1.entrySet()) {
val1 = entry.getKey();
}
for (Map.Entry<String, String> entry : map2.entrySet()) {
val2 = entry.getKey();
}
return val1.compareTo(val2);
}
});
for (Map<String, String> hashMap : list) {
for (Map.Entry<String, String> entry : hashMap.entrySet()) {
System.out.println(entry.getKey() + "/" + entry.getValue());
}
}
}
public static int randInt(int min, int max) {
Random rand = new Random();
int randomNum = rand.nextInt((max - min) + 1) + min;
return randomNum;
}
}
它打印输出-
10/Values10:1437660285301
11/Values11:1437660285301
11/Values11:1437660285301
11/Values11:1437660285301
13/Values13:1437660285301
13/Values13:1437660285301
15/Values15:1437660285301
15/Values15:1437660285301
15/Values15:1437660285301
16/Values16:1437660285301
17/Values17:1437660285301
18/Values18:1437660285301
18/Values18:1437660285301
19/Values19:1437660285301
19/Values19:1437660285301
2/Values2:1437660285301
3/Values3:1437660285301
4/Values4:1437660285301
6/Values6:1437660285301
6/Values6:1437660285301
它按键对值进行分组,但我想要整个排序列表,如上例所示。
我期待 2,然后是 3,然后是 4,然后继续。
最佳答案
您正在根据类型为 String
的键进行比较。比较将按字典顺序进行,即 12
小于 2
。
您需要在比较器中将键作为 Integers
进行比较:
Collections.sort(list, new Comparator<Map<String, String>>() {
@Override
public int compare(Map<String, String> map1,
Map<String, String> map2) {
String val1 = "";
String val2 = "";
for (Map.Entry<String, String> entry : map1.entrySet()) {
val1 = entry.getKey();
}
for (Map.Entry<String, String> entry : map2.entrySet()) {
val2 = entry.getKey();
}
return Integer.valueOf(val1).compareTo(Integer.valueOf(val2));
}
});
关于java - 如何按升序对映射字符串列表进行排序,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31589854/