getOrDefault method in Java

By Harish Gowda | | 2 minutes

In this tutorial we will learn how to use getOrDefault method in Java.

Introduction

getOrDefault is present in Map interface to get value for a given key and return a default value if the key is not present.

It helps to prevent NullPointerException when retrieving values from the Map.

Below is snippet code of getOrDefault

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default V getOrDefault(Object key, V defaultValue) {
    V v;
    return (((v = get(key)) != null) || containsKey(key))
    ? v
    : defaultValue;
}

In the below example we get null as return value if the key is not present.

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package examples;

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

public class App {

    public static void main(String[] args) {

        Map<String,Integer> data = new HashMap<>();
        data.put("Sydney",200);
        data.put("Tokyo",300);
        System.out.println(data.get("Paris")); // null

    }
}

To avoid this we can use getOrDefault which returns the default value as 0 if the key is not present. This helps us to avoid writing extra check for null values.

If the key is present it return the corresponding value as shown below.

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package examples;

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

public class App {

    public static void main(String[] args) {

        Map<String,Integer> data = new HashMap<>();
        data.put("Sydney",200);
        data.put("Tokyo",300);
        System.out.println(data.getOrDefault("Paris",0)); // 0
        System.out.println(data.getOrDefault("Sydney",0)); //200

    }
}

Use Case

In the below use case we can use getOrDefault to provide default message/response when the key is not present.

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package examples;

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

public class App {

    public static void main(String[] args) {

        Map<Integer,String> data = new HashMap<>();
        data.put(404,"Not Found");
        data.put(403,"Forbidden");

        int errorCode=600;
        System.out.println(data.getOrDefault(errorCode,"Unknown Error"));
        //Unknown Error
    }
}

Conclusion

  1. getOrDefault method simplifies getting key and default value handling.
  2. Prevents NullPointerException by returning default value.
  3. It is helpful in providing default message/reponse for a given key.