Практика за 8й урок.

Java4L8HW/src/alexrm84/ChainsHashTableImplement.java

@@ -0,0 +1,106 @@
+package alexrm84;
+
+import java.util.LinkedList;
+
+public class ChainsHashTableImplement implements HashTable {
+
+    public static final Integer INVALID_COST = null;
+
+    private class Entry{
+        private Item key;
+        private int value;
+
+        public Entry(Item key, int value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return "Entry{" +
+                    "key=" + key +
+                    ", value=" + value +
+                    '}';
+        }
+    }
+
+    private LinkedList<Entry>[] data;
+    private int size;
+    private int maxSize;
+
+    public ChainsHashTableImplement(int maxSize) {
+        this.data = new LinkedList[maxSize];
+        this.maxSize = maxSize;
+    }
+
+    private int hashFunc(int key){
+        return key % data.length;
+    }
+
+    @Override
+    public boolean put(Item item, Integer cost) {
+        int index = hashFunc(item.hashCode());
+        if (data[index]==null){
+            data[index] = new LinkedList<>();
+        }
+        boolean check = true;
+        for (Entry entry:data[index]) {
+            if (entry.key.equals(item)){
+                entry.value=cost;
+                check=false;
+            }
+        }
+        if (check){
+            data[index].add(new Entry(item,cost));
+            size++;
+        }
+        return true;
+    }
+
+    @Override
+    public Integer get(Item item) {
+        int index = hashFunc(item.hashCode());
+        for (Entry entry:data[index]) {
+            if (entry.key.equals(item)){
+                return entry.value;
+            }
+        }
+        return INVALID_COST;
+    }
+
+    @Override
+    public boolean remove(Item item) {
+        int index = hashFunc(item.hashCode());
+        for (Entry entry:data[index]) {
+            if (entry.key.equals(item)){
+                data[index].remove(entry);
+                size--;
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public int getSize() {
+        return size;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return size==0;
+    }
+
+    @Override
+    public void display() {
+        System.out.println("------------------------------");
+        for (int i = 0; i < data.length; i++) {
+            if (data[i]!=null){
+                for (Entry entry:data[i]) {
+                    System.out.println(String.format("%d = [%s]",i,entry));
+                }
+            }
+        }
+        System.out.println("------------------------------");
+    }
+}

Java4L8HW/src/alexrm84/DoubleHashTableImplement.java

@@ -0,0 +1,18 @@
+package alexrm84;
+
+public class DoubleHashTableImplement extends HashTableImplement{
+    private static int DOUBLE_HASH_CONST = 5;
+
+    public DoubleHashTableImplement(int maxSize) {
+        super(maxSize);
+    }
+
+    @Override
+    protected int getStep(int key) {
+        return HashFuncDouble(key);
+    }
+
+    private int HashFuncDouble(int key) {
+        return DOUBLE_HASH_CONST -(key% DOUBLE_HASH_CONST);
+    }
+}

Java4L8HW/src/alexrm84/HashTable.java

@@ -0,0 +1,11 @@
+package alexrm84;
+
+public interface HashTable {
+
+    boolean put(Item item, Integer cost);
+    Integer get(Item item);
+    boolean remove(Item item);
+    int getSize();
+    boolean isEmpty();
+    void display();
+}

Java4L8HW/src/alexrm84/HashTableImplement.java

@@ -0,0 +1,112 @@
+package alexrm84;
+
+
+public class HashTableImplement implements HashTable {
+
+    public static final int INVALID_INDEX = -1;
+    public static final Integer INVALID_COST = null;
+
+    class Entry{
+        private Item key;
+        private int value;
+
+        public Entry(Item key, int value) {
+            this.key = key;
+            this.value = value;
+        }
+
+        @Override
+        public String toString() {
+            return "Entry{" +
+                    "key=" + key +
+                    ", value=" + value +
+                    '}';
+        }
+    }
+
+    private Entry[] data;
+    private int size;
+    private int maxSize;
+
+    public HashTableImplement(int maxSize) {
+        this.data = new Entry[maxSize*2];
+        this.maxSize = maxSize;
+    }
+
+    private int hashFunc(int key){
+        return key % data.length;
+    }
+
+    @Override
+    public boolean put(Item item, Integer cost) {
+        if (size==maxSize){
+            return false;
+        }
+        int index = hashFunc(item.hashCode());
+        while (data[index]!=null){
+            index+=getStep(item.hashCode());
+            index%=data.length;
+        }
+        data[index] = new Entry(item,cost);
+        return true;
+    }
+
+    protected int getStep(int key){
+        return 1;
+    }
+
+    @Override
+    public Integer get(Item item) {
+        int index = indexOf(item);
+        if (index == INVALID_INDEX){
+            return INVALID_COST;
+        }else {
+            return data[index].value;
+        }
+    }
+
+    private int indexOf(Item item){
+        int index = hashFunc(item.hashCode());
+        int count=0;
+        while (data[index]!=null && count<=data.length){
+            if (data[index].key.equals(item)){
+                return index;
+            }
+            index+=getStep(item.hashCode());
+            index%=data.length;
+            count++;
+        }
+        return INVALID_INDEX;
+    }
+
+    @Override
+    public boolean remove(Item item) {
+        int index = indexOf(item);
+        if (index!=INVALID_INDEX){
+            data[index]=null;
+            size--;
+            return true;
+        }else {
+            return false;
+        }
+    }
+
+    @Override
+    public int getSize() {
+        return size;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return size==0;
+    }
+
+    @Override
+    public void display() {
+        System.out.println("------------------------------");
+        for (int i = 0; i < data.length; i++) {
+            System.out.println(String.format("%d = [%s]",i,data[i]));
+        }
+        System.out.println("------------------------------");
+    }
+}

Java4L8HW/src/alexrm84/Item.java

@@ -0,0 +1,44 @@
+package alexrm84;
+
+import java.util.Objects;
+
+public class Item {
+
+    private final String title;
+    private final int id;
+
+    public Item(int id, String title) {
+        this.title = title;
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (o == null || getClass() != o.getClass()) return false;
+        Item item = (Item) o;
+        return id == item.id &&
+                Objects.equals(title, item.title);
+    }
+
+    @Override
+    public int hashCode() {
+        return id;//Objects.hash(id);
+    }
+
+    @Override
+    public String toString() {
+        return "Item{" +
+                "title='" + title + '\'' +
+                ", id=" + id +
+                '}';
+    }
+}

Java4L8HW/src/alexrm84/Main.java

@@ -0,0 +1,25 @@
+package alexrm84;
+
+public class Main {
+
+    public static void main(String[] args) {
+
+//        HashTable hashTable = new HashTableImplement(5);
+//        HashTable hashTable = new DoubleHashTableImplement(5);
+        HashTable hashTable = new ChainsHashTableImplement(5);
+        hashTable.put(new Item(1,  "Orange"), 150);
+        hashTable.put(new Item(77, "Banana"), 100);
+        hashTable.put(new Item(62, "Lemon"), 250);
+        hashTable.put(new Item(21, "Potato"), 67);
+        hashTable.put(new Item(55, "Milk"), 120);
+
+        System.out.println("Size is " + hashTable.getSize());
+        hashTable.display();
+
+        System.out.println("Cost potato is " + hashTable.get(new Item(21, "Potato")));
+        System.out.println("Cost Banana is " + hashTable.get(new Item(77, "Banana")));
+
+        hashTable.remove(new Item(77, "Banana"));
+        System.out.println("Cost Banana is " + hashTable.get(new Item(77, "Banana")));
+    }
+}