How to reduce time-complexity in "put" function

Question

I'm trying to find a way to make my algorithm execute faster. What this function is currently doing is inserting values(chars) and keys(strings) into my hashtable with 7 slots. It is also running checks to see if A. there is something occupying it's optimal slot, and then placing it in the best available spot. And B. If 2 identical keys are inserted, the new key simply transfers it's value to the old key instead of taking up a new slot by itself. Is there any way to do this without iterating my "keys" array?

public void put(String key, Character val) {
                            int z = hash(key);
                            while(keys[z] != null){
                                if(key.equals(keys[z])){
                                    vals[z]= val;
                                    break;
                                }

                                z ++;
                                if (z>6){
                                    z=0;
                                    if(key.equals(keys[z])){  
                                        vals[z]= val;
                                        break;
                                    }
                                    if(keys[0]==null){
                                    break;
                                    }
                                    else{
                                        z++;
                                    }
                                }
                            }
                            keys[z] = key;
                            vals[z] = val;
                            N += 1;

                        } 

update: This is my hash() function

public int hash(String key) {
                            int i;
                            int v = 0;

                            for (i = 0; i < key.length(); i++) {
                                v += key.charAt(i);
                            }
                            return v % M;
                        }

Answer 1

If I understand your code right you have an open-addressed hash table with linear probing .

Alternatives for linear probing (your loop where you're searching for an empty spot) are:

• https://en.m.wikipedia.org/wiki/Double_hashing
• https://en.m.wikipedia.org/wiki/Quadratic_probing

But anyway worst-case time will be linear. And for a very small table with only 7 elements your linear approach with increments by 1 looks fine.