Java Check if key exists in HashMap
摘要: In Java, you can use Map.containsKey() to check if a key exists in a Map.
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
References
