CODEWITHSUNDEEP
javaarraylistdata-structureshashhashmap
jia chen
jia chen

Reputation: 760

Custom hashmap with 2 value fields VS implement a hashmap with an array as value in java

Are they added benefits to writing my own hash map data structure instead of using a pre written class like hashmap in java.

Background. Im writing a spring application that requires data structure that can map a single key to map to two values.

the current benefits i can think of now will be: - can include more methods such as swap (swap value 1 with 2) - more control over hashing functions - more control in general

was wondering: - if they are any draw backs in terms of performance or complexity - or if it makes any sense at all to write my own data structure

Thanks for taking the time to read.

EDIT: If it helps helps. i only need fast access speed (methods like get and contains) for methods that "put", time taken can be a little longer Any suggestion on what i should do?

Upvotes: 2

Views: 206

Answers (2)

Bohemian
Bohemian

Reputation: 424983

Keep it simple: Use HashMap whose value type is a simple class to hold two values, eg (for simplicity, I have assumed key and both values are String):

class Pair {
    private String a;
    private String b;
    public Pair(String a, String b) {
        this.a = a;
        this.b = b;
    }
    public String getA() {
        return a;
    }
    public String getB() {
        return b;
    }
    public void swap() {
        // Note: Not threadsafe
        String tmp = a;
        a = b;
        b = tmp;
    }
    public boolean equals(Object o) {
        return o instanceof Pair
            && Objects.equals(a, ((Pair)o).a
            && Objects.equals(b, ((Pair)o).b;
    }
    public int hashCode() {
        return Objects.hash(a, b);
    }
}

Map<String, Pair> map = new HashMap<>();

Upvotes: 2

Keith
Keith

Reputation: 3151

You risk missing out on a very well-vetted, proven and durable framework by not using the java.util package. No offense, but it's unlikely you're going to come up with a better design and implementation, especially one as bug-free and optimized as part of Java's core API. Rather, use what exists and either write your own small methods, extend the existing HashMap, or find another open-source variant (e.g. maybe from Apache FastHashMap) to get the additional required functionality.

Upvotes: 1

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