HashTable in Java

public class SimpleHashing {

// Number of buckets by default in the list.
private static final int BUCKETS_DEFAULT = 16;
// Array of buckets.
private HashNode[] buckets;
// The actual number of buckets.
private int numBuckets;
// number of elements int he hash table.
private int size;

// A linked-list type class that holds the keys and values of the hash table.
private static class HashNode {
    String key;
    String value;
    HashNode next;
    
    public HashNode(String key, String value) {
        this.key = key;
        this.value = value;
        this.next = null;
    }
    
    // Bonus constructor that allows for assigning the next hash node.
    public HashNode(String key, String value, HashNode next) {
        this.key = key;
        this.value = value;
        this.next = next;
    }
}

// Parameter-less constructor.
public SimpleHashing() {
    this(BUCKETS_DEFAULT);
}

// Constructor with defined number of buckets for the hash table.
public SimpleHashing(int numBuckets) {
    this.numBuckets = numBuckets;
    buckets = new HashNode[numBuckets];
}

public boolean isEmpty() {
    return size <= 0;
}

private int getHash(String key) {
    // Use the hashCode function of String, mod the size of the list.
    // using a shift mask to ensure the value is positive (and faster than Math.abs)
    return (key.hashCode() & 0x7fffffff) % numBuckets;
}

public void put(String key, String value) {
    int bucket = getHash(key);
    HashNode newNode = new HashNode(key, value);
    if(buckets[bucket] == null) {
        buckets[bucket] = newNode;
        size++;
    } else {
        HashNode tmp = buckets[bucket];
        while(tmp.next != null) {
            if(tmp.key.equals(key)) {
                tmp.value = value;
                return;
            }
            tmp = tmp.next;
        }
        tmp.next = newNode;
        size++;
    }
    return;
}

public String get(String key) {
    int bucket = getHash(key);
    HashNode tmp = buckets[bucket];
    while(tmp != null) {
        if(tmp.key.equals(key)) {
            return tmp.value;
        }
        tmp = tmp.next;
    }
    return null;
}

public boolean contains(String key) {
    int bucket = getHash(key);
    HashNode tmp = buckets[bucket];
    while(tmp != null) {
        if(tmp.key.equals(key)) {
            return true;
        }
        tmp = tmp.next;
    }
    return false;
}

public void remove(String key) {
    int bucket = getHash(key);
    if(buckets[bucket] == null) {
        return;
    }
    HashNode tmp = buckets[bucket];
    if(tmp.key.equals(key)) {
        buckets[bucket] = buckets[bucket].next;
        size--;
        return;
    }
    while(tmp.next != null) {
        if(tmp.next.key.equals(key)) {
            tmp.next = tmp.next.next;
            size--;
            return;
        }
        tmp = tmp.next;
    }
}

// Clears all the keys and values on the hash table.
public void clear() {
    buckets = new HashNode[numBuckets];
}

public int size() {
    return size;
}

public String toString() {
    StringBuilder res = new StringBuilder();
    int count = 0;
    res.append("{ ");
    for(int i = 0; i < numBuckets; i++) {
        if(buckets[i] != null) {
            HashNode tmp = buckets[i];
            while(tmp != null) {
                res.append(tmp.key + ": " + tmp.value);
                count++;
                if(count < size) {
                    res.append(", ");
                }
                tmp = tmp.next;
            }    
        }
    }    
    res.append(" }");
    return res.toString();
}

public static void main(String[] args) {
    SimpleHashing hashTable = new SimpleHashing(32);
    hashTable.put("Hello", "World");
    hashTable.put("Goodbye", "Cruel world");
    hashTable.put("Wonderful", "Weather");
    hashTable.put("Who's", "There");
    hashTable.put("It's a'", "Me");
    
    System.out.println(hashTable.toString());
    System.out.println(hashTable.contains("Goodbye"));
    hashTable.remove("Goodbye");
    System.out.println(hashTable.contains("Goodbye"));
    
    System.out.println(hashTable.toString());
}

}