In Java, you can use Map.containsKey() to check if a key exists in a Map.
TestMap.java
package com.mkyong.examples;
import java.util.HashMap;
import java.util.Map;
public class TestMap {
public static void main(String[] args) {
Map<String, Integer> fruits = new HashMap<>();
fruits.put("apple", 1);
fruits.put("orange", 2);
fruits.put("banana", 3);
fruits.put("watermelon", null);
System.out.println("1. Is key 'apple' exists?");
if (fruits.containsKey("apple")) {
//key exists
System.out.println("yes! - " + fruits.get("apple"));
} else {
//key does not exists
System.out.println("no!");
}
System.out.println("\n2. Is key 'watermelon' exists?");
if (fruits.containsKey("watermelon")) {
System.out.println("yes! - " + fruits.get("watermelon"));
} else {
System.out.println("no!");
}
}
}
Output
1. Is key 'apple' exists?
yes! - 1
2. Is key 'watermelon' exists?
yes! - null
Incorrect. “get” will return null if the key exists and maps to null or if the key does not exist. “getEntry” will return null only if the key does not exist.
Thanks for your inputs, article is updated. To avoid confusion, it is better stay with the proven Map.containsKey().