Lear Java HashMap – Store Different Value Types

Java HashMap – Store Different Value Types

In Java, the HashMap is an important data structure that allows us to store data in key-value pairs. This means the data is stored in the form of a specific key associated with its corresponding value. Usually, the HashMap will have objects as keys and values, but what if we need to store different value types in the same map? Fortunately, there are several ways to do this in Java. Let’s take a look at how to use the HashMap to store different value types.

Using Generics

One way to store different value types in a HashMap is by using generics. Generics allow us to define a generic type definition at compile-time that can be used anywhere in our code. This means that we can specify the type of object we want to use as the key or value when creating the HashMap. For example, we could create a HashMap with string keys and double values by defining the generic types as such:

HashMap&ltString, Double&gt  myMap = new HashMap&ltString, Double&gt();

This ensures that we don’t accidentally put a value of the wrong type into our map.

Using Object Type

Another way to store different value types in the same HashMap is to use the Object type. With the Object type, we can declare the HashMap without any specified generics and then manually assign each value’s type when we add it to the map. For example:

HashMap myMap = new HashMap();
myMap.put("key1", 123); //integer
myMap.put("key2", "abc"); //string
myMap.put("key3", 1.23); //double
myMap.put("key4", true); //boolean

Using the Object type for our HashMap is not recommended, however, since it can cause type-safety issues down the line. It’s always better to use generics if possible.

Conclusion

In this tutorial, we looked at two different ways to store different value types in a HashMap in Java. First, we discussed how to use generics to define the types of the key and value. And second, we looked at how to use the Object type to assign values to the map. Knowing how to store different value types in a HashMap is an important skill that every Java developer should have. With the methods discussed in this tutorial, you should be well on your way.