Java generic method: Print key-value pairs in a map

Last update on May 19 2025 13:13:05 (UTC/GMT +8 hours)

7. Print Generic Map Entries

Write a Java program to create a generic method that takes a map of any type and prints each key-value pair.

Sample Solution:

Java Code:

// Print_map_elements.java
// Print_map_elements Class

import java.util.HashMap;
import java.util.Map;

public class Print_map_elements {

  public static > K, V > void printMap(Map > K, V > map) {
    for (Map.Entry > K, V > entry: map.entrySet()) {
      K key = entry.getKey();
      V value = entry.getValue();
      System.out.println("Key: " + key + ", Value: " + value);
    }
  }

  public static void main(String[] args) {
    Map > String, Integer > colorMap = new HashMap > > ();
    colorMap.put("Red", 1);
    colorMap.put("Green", 2);
    colorMap.put("Blue", 3);

    System.out.println("Color Map:");
    printMap(colorMap);

    Map > String, String > capitalMap = new HashMap > > ();
    capitalMap.put("Germany ", "Berlin");
    capitalMap.put("USA", "Washington, D.C.");
    capitalMap.put("UK", "London");
    capitalMap.put("France", "Paris");

    System.out.println("\nCapital Map:");
    printMap(capitalMap);
  }
}

Sample Output:

Color Map:
Key: Red, Value: 1
Key: Blue, Value: 3
Key: Green, Value: 2

Capital Map:
Key: Germany , Value: Berlin
Key: USA, Value: Washington, D.C.
Key: UK, Value: London
Key: France, Value: Paris

Explanation:

In the above exercise, we define a generic method printMap() that takes a map "map" as input. The method iterates over the map's key-value pairs using a for-each loop and Map.Entry. For each entry, it retrieves the key and value using the getKey() and getValue() methods respectively. It then prints the key-value pair using System.out.println().

In the main() method, we demonstrate the printMap() method by passing a ColorMap containing mappings of number names to their values. We also pass a capitalMap containing mappings of country names to their capitals. We call the printMap() method for each map to print their respective key-value pairs.

Flowchart:

Flowchart: Java generic method: Print key-value pairs in a map.

For more Practice: Solve these Related Problems:

Write a Java program to create a generic method that prints the key-value pairs of a map in ascending order based on keys.
Write a Java program to create a generic method that iterates over a map and prints each entry formatted as "key -> value" using Java 8 streams.
Write a Java program to create a generic method that prints key-value pairs from a map, highlighting entries that satisfy a specific condition.
Write a Java program to create a generic method that prints the key-value pairs of a map in reverse order of their natural key ordering.

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