create 0706 in java

Author: Mohammed785

Diff for: java/0706-design-hashmap.java

@@ -0,0 +1,44 @@
+class ListNode {
+    int key, val;
+    ListNode next;
+    public ListNode(int key, int val, ListNode next) {
+        this.key = key;
+        this.val = val;
+        this.next = next;
+    }
+}
+class MyHashMap {
+    static final int size = 19997;
+    static final int mult = 12582917;
+    ListNode[] data;
+    public MyHashMap() {
+        this.data = new ListNode[size];
+    }
+    private int hash(int key) {
+        return (int)((long)key * mult % size);
+    }
+    public void put(int key, int val) {
+        remove(key);
+        int h = hash(key);
+        ListNode node = new ListNode(key, val, data[h]);
+        data[h] = node;
+    }
+    public int get(int key) {
+        int h = hash(key);
+        ListNode node = data[h];
+        for (; node != null; node = node.next)
+            if (node.key == key) return node.val;
+        return -1;
+    }
+    public void remove(int key) {
+        int h = hash(key);
+        ListNode node = data[h];
+        if (node == null) return;
+        if (node.key == key) data[h] = node.next;
+        else for (; node.next != null; node = node.next)
+            if (node.next.key == key) {
+                node.next = node.next.next;
+                return;
+            }
+    }
+}