One to One Mapping in Java

OneToOneMap.java

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

/**
 * Created by [email protected] on 9/1/18.
 *
 * Preliminary idea .. not all Map related stuff are implemented. 
 * Tested with a Long and Integer.
 * 
 * if new value value is set for a key, in addition to updating key->value mapping,
 * the old value -> key mapping is removed and new value-> key is added. Same goes for 
 * updating key vor a value.
 * 
 * As the behaviour is same on both sides, instead of claling them key and value, 
 * we call them A and B
 * 
 */

public class OneToOneMap<Type1, Type2> {
    private Map<Type1, Type2> map_a2b;
    private Map<Type2, Type1> map_b2a;

    public OneToOneMap() {
        map_a2b = new HashMap<>();
        map_b2a = new HashMap<>();
    }

    public Type2 getFromA(Type1 key) {
        return map_a2b.get(key);
    }

    public Type1 getFromB(Type2 key) {
        return map_b2a.get(key);
    }

    public void putInA(Type1 key, Type2 value) {
        if (map_a2b.containsKey(key)) {
            map_b2a.remove(map_a2b.get(key));
        }
        map_a2b.put(key, value);
        map_b2a.put(value, key);
    }

    public void putInB(Type2 key, Type1 value) {
        if (map_b2a.containsKey(key)) {
            map_a2b.remove(map_b2a.get(key));
        }
        map_b2a.put(key, value);
        map_a2b.put(value, key);
    }

    public boolean aContains(Type1 key){
        return map_a2b.containsKey(key);
    }

    public boolean bContains(Type2 key){
        return map_b2a.containsKey(key);
    }

    public void removeFromA(Type1 key){
        map_b2a.remove(map_a2b.get(key));
        map_a2b.remove(key);
    }

    public void removeFromB(Type2 key){
        map_a2b.remove(map_b2a.get(key));
        map_b2a.remove(key);
    }
}