solved Task 3

src/ch/zhaw/ads/MyHashtable.java

@@ -1,13 +1,11 @@
 package ch.zhaw.ads;
 
-import java.util.Collection;
+import java.util.*;
-import java.util.Map;
-import java.util.Set;
 
 @SuppressWarnings("unchecked")
 public class MyHashtable<K, V> implements Map<K, V> {
-    private K[] keys = (K[]) new Object[10];
+    private K[] keys;// = (K[]) new Object[10];
-    private V[] values = (V[]) new Object[10];
+    private V[] values;// = (V[]) new Object[10];
 
     private int hash(Object k) {
         int h = Math.abs(k.hashCode());
@@ -16,36 +14,97 @@ public class MyHashtable<K, V> implements Map<K, V> {
 
     public MyHashtable(int size) {
         // to be done
+        keys = (K[]) new Object[size];
+        values = (V[]) new Object[size];
+    }
+
+    public MyHashtable() {
+        clear();
     }
 
     // Removes all mappings from this map (optional operation).
     public void clear() {
         // to be done
-        throw new UnsupportedOperationException();
+        keys = (K[]) new Object[1000];
+        values = (V[]) new Object[1000];
     }
 
     // Associates the specified value with the specified key in this map (optional operation).
     public V put(K key, V value) {
         // to be done
-        throw new UnsupportedOperationException();
+        if(size() >= keys.length) {
+            throw new IllegalStateException("Overflow");
+        } else {
+            int i = -1;
+            int hashCode = hash(key);
+            int index;
+            do {
+                i++;
+                index = (hashCode + i) % keys.length;
+            } while (keys[index] != null && !keys[index].equals(key));
+            keys[index] = key;
+            values[index] = value;
+        }
+        return value;
     }
 
     // Returns the value to which this map maps the specified key.
     public V get(Object key) {
         // to be done
-        throw new UnsupportedOperationException();
+        int i = -1;
+        int hashCode = hash(key);
+        int index;
+        do {
+            i++;
+            index = (hashCode + i) % keys.length;
+        } while (keys[index] != null && !(keys[index].equals(key)));
+        return values[index];
     }
 
     // Removes the mapping for this key from this map if present (optional operation).
     public V remove(Object key) {
         // to be done (Aufgabe 3)
-        throw new UnsupportedOperationException();
+        int i = -1;
+        int hashCode = hash(key);
+        int index;
+        do {
+            i++;
+            if(i >= keys.length){
+                return null;
+            }
+            index = (hashCode + i) % keys.length;
+        } while (keys[index] != null && !(keys[index].equals(key)));
+        V toReturn = values[index];
+        keys[index] = null;
+        values[index] = null;
+        List<K> keysToRehash = new ArrayList<>();
+        List<V> valuesToRehash = new ArrayList<>();
+        i++;
+        index = (hashCode + i) % keys.length;
+        while(keys[index] != null) {
+            keysToRehash.add(keys[index]);
+            valuesToRehash.add(values[index]);
+            keys[index] = null;
+            values[index] = null;
+            i++;
+            index = (hashCode + i) % keys.length;
+        }
+        for(int indexToRehash = 0; indexToRehash < keysToRehash.size(); indexToRehash++){
+            put(keysToRehash.get(indexToRehash), valuesToRehash.get(indexToRehash));
+        }
+        return toReturn;
     }
 
     // Returns the number of key-value mappings in this map.
     public int size() {
         // to be done
-        throw new UnsupportedOperationException();
+        int counter = 0;
+        for(K key : keys) {
+            if(key != null){
+                counter++;
+            }
+        }
+        return counter;
     }
 
     // UnsupportedOperationException ===================================================================