Generic BiDiMap

Question

I have a BiDiMap class. How can I make it generic, by accepting not only String but also Object type of objects as input parameters, with keeping all the original functions working. For example I'd like to be able to use function put() with Object, Object as input parameters instead of String, String. I'd like to change all the input parameters and returning values of String type to Object types.

package MyBiDiMap;

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

public class BiDiMap {

    private Map<String, String> keyValue;
    private Map<String, String> valueKey;

    public BiDiMap() {
        this.keyValue = new HashMap<>();
        this.valueKey = new HashMap<>();
    }

    private BiDiMap(Map<String, String> keyValue,
            Map<String, String> valueKey) {
        this.keyValue = keyValue;
        this.valueKey = valueKey;
    }

    public void put(String key, String value) {
        if (this.keyValue.containsKey(key)
                || this.valueKey.containsKey(value)) {
            this.remove(key);
            this.removeInverse(value);
        }
        this.keyValue.put(key, value);
        this.valueKey.put(value, key);
    }

    public String get(String key) {
        return this.keyValue.get(key);
    }

    public String getInverse(String value) {
        return this.valueKey.get(value);
    }

    public void remove(String key) {
        String value = this.keyValue.remove(key);
        this.valueKey.remove(value);
    }

    public void removeInverse(String value) {
        String key = this.valueKey.remove(value);
        this.keyValue.remove(key);
    }

    public int size() {
        return this.keyValue.size();
    }

    public BiDiMap getInverse() {
        return new BiDiMap(this.valueKey, this.keyValue);
    }
}

Answer 1

The answer is pretty simple: by introducing two generic types, named K and V on your class and by then vigorously replacing all occurance of String with K (where your key type should be used), and similarly with V where values are required.

In other words: don't use specific types when declaring the two maps, but in all places, use the new generic types you added on class level.