EN
Java - sort HashMap by keys
7 points
Short solution:
xxxxxxxxxx1
Map<String, Integer> map = new HashMap<>();2
// put key / value to map3
4
// to sort map we use tree map and default String comparator5
Map<String, Integer> sortedMap = new TreeMap<>();6
sortedMap.putAll(map);7
8
sortedMap.forEach((key, value) -> {9
System.out.println("Key: " + key + ", Value : " + value);10
});Another short solution:
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Map<String, Integer> map = new HashMap<>();2
// put key / value to map3
4
List<String> sortedKeys = new ArrayList<>(map.keySet());5
Collections.sort(sortedKeys);6
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// we iterate over sorted keys and get from map in sorted order8
for (String key : sortedKeys) {9
Integer value = map.get(key);10
System.out.println("Key: " + key + ", Value : " + value);11
}xxxxxxxxxx1
import java.util.HashMap;2
import java.util.Map;3
import java.util.TreeMap;4
5
public class Example1 {6
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public static void main(String[] args) {8
9
Map<String, Integer> map = new HashMap<>();10
map.put("YY", 3);11
map.put("ZZ", 4);12
map.put("CC", 2);13
map.put("AA", 1);14
15
System.out.println("Unsorted:");16
map.forEach((key, value) -> {17
System.out.println("Key: " + key + ", Value : " + value);18
});19
20
System.out.println("---------");21
22
// to sort map we use tree map and default String comparator23
Map<String, Integer> sortedMap = new TreeMap<>();24
sortedMap.putAll(map);25
26
System.out.println("Sorted:");27
sortedMap.forEach((key, value) -> {28
System.out.println("Key: " + key + ", Value : " + value);29
});30
}31
}Output:
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Unsorted:2
Key: YY, Value : 33
Key: ZZ, Value : 44
Key: CC, Value : 25
Key: AA, Value : 16
---------7
Sorted:8
Key: AA, Value : 19
Key: CC, Value : 210
Key: YY, Value : 311
Key: ZZ, Value : 4xxxxxxxxxx1
import java.util.*;2
3
public class Example2 {4
5
public static void main(String[] args) {6
7
Map<String, Integer> map = new HashMap<>();8
map.put("YY", 3);9
map.put("ZZ", 4);10
map.put("CC", 2);11
map.put("AA", 1);12
13
System.out.println("Unsorted:");14
map.forEach((key, value) -> {15
System.out.println("Key: " + key + ", Value : " + value);16
});17
18
System.out.println("---------");19
20
List<String> sortedKeys = new ArrayList<>(map.keySet());21
Collections.sort(sortedKeys);22
23
System.out.println("Sorted:");24
// we iterate over sorted keys and get from map in sorted order25
for (String key : sortedKeys) {26
Integer value = map.get(key);27
System.out.println("Key: " + key + ", Value : " + value);28
}29
}30
}Output:
xxxxxxxxxx1
Unsorted:2
Key: YY, Value : 33
Key: ZZ, Value : 44
Key: CC, Value : 25
Key: AA, Value : 16
---------7
Sorted:8
Key: AA, Value : 19
Key: CC, Value : 210
Key: YY, Value : 311
Key: ZZ, Value : 4
