How to find the Entry with largest Key in a Java Map Collection
Given a map in Java, the task is to find out the entry in this map with the highest key.
Examples:
Input: Map = {ABC = 10, DEF = 30, XYZ = 20}
Output: XYZ = 20
Input: Map = {1 = 40, 2 = 30, 3 = 60}
Output: 3 = 60
Approach
Iterate the map entry by entry
for (Map.Entry entry : map.entrySet())
{
// Operations
}
Store the first entry in a reference variable to compare to initially.
If the current entry’s key is greater than the reference entry’s value, then store the current entry as the reference entry.
Repeat this process for all the entries in the map.
In the end, the reference variable has the required entry with the highest key in the map.
Print this entry
Below is the implementation of the above approach:
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// Java program to find entry
// with highest key in a map
import java.util.*;
public class GFG {
// Find the entry with highest key
public static <K extends Comparable<K>, V> Map.Entry<K, V>
getMaxEntryInMapBasedOnKey(Map<K, V> map)
{
// To store the result
Map.Entry<K, V> entryWithMaxKey = null;
// Iterate in the map to find the required entry
for (Map.Entry<K, V> currentEntry : map.entrySet()) {
if (
// If this is the first entry,
// set the result as this
entryWithMaxKey == null
// If this entry's key is more than the max key
// Set this entry as the max
|| currentEntry.getKey()
.compareTo(entryWithMaxKey.getKey())
> 0) {
entryWithMaxKey = currentEntry;
}
}
// Return the entry with highest key
return entryWithMaxKey;
}
// Print the map
public static void print(Map<String, Integer> map)
{
System.out.print("Map: ");
// If map does not contain any value
if (map.isEmpty()) {
System.out.println("[]");
}
else {
System.out.println(map);
}
}
// Driver code
public static void main(String[] args)
{
Map<String, Integer> map
= new HashMap<>();
map.put("ABC", 10);
map.put("DEF", 30);
map.put("XYZ", 20);
print(map);
System.out.println(
"Entry with highest key: "
+ getMaxEntryInMapBasedOnKey(map));
}
}
Output:
Map: {ABC=10, DEF=30, XYZ=20}
Entry with highest key: XYZ=20
