Check if a value exists in a Map in Java

This post will discuss how to check if a value exists in a Map in Java. A value value exists in the map if it contains at least one mapping to a value v for which Objects.equals(value, v) holds.

1. Using `containsValue()` method

The standard solution to check if a value exists in a map is using the containsValue() method, which returns true if the map maps one or more keys to the specified value.

import java.util.HashMap;

import java.util.Map;

public class Main

{

public static void main(String[] args)

{

Map<Character, Integer> hashMap = new HashMap<>();

for (int i = 65; i <= 90; i++) {

hashMap.put((char) i, i);

}

int value = 70;

boolean isExists = hashMap.containsValue(value);

System.out.println(isExists); // true

}

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Note that if the value is an custom object, remember to override the equals and hashCode methods of that class.

2. Using `anyMatch()` method

The idea is to get the collection of the values contained in the map, and then search the specified value in that collection. This can be done in a single line using Stream API:

import java.util.HashMap;

import java.util.Map;

public class Main

{

public static void main(String[] args)

{

Map<Character, Integer> hashMap = new HashMap<>();

for (int i = 65; i <= 90; i++) {

hashMap.put((char) i, i);

}

int value = 70;

boolean isExists = hashMap.values().stream().anyMatch(v -> v == value);

System.out.println(isExists); // true

}

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3. Using for loop

Before Java 8, you can write a custom routine to determine if a value exists in a Map or not. Here’s a working example:

import java.util.HashMap;

import java.util.Map;

public class Main

{

public static void main(String[] args)

{

Map<Character, Integer> hashMap = new HashMap<>();

for (int i = 65; i <= 90; i++) {

hashMap.put((char) i, i);

}

int value = 70;

boolean isExists = false;

for (Integer v: hashMap.values()) {

if (v == value) {

isExists = true;

break;

}

System.out.println(isExists); // true

}

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That’s all about checking if a value exists in a Map in Java.

Check if a value exists in a Map in Java

1. Using containsValue() method

2. Using anyMatch() method

3. Using for loop

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1. Using `containsValue()` method

2. Using `anyMatch()` method