implemented a stack in java

Author: PaddyKe

contents/stacks_and_queues/code/java/Stack.java

@@ -0,0 +1,72 @@
+import java.util.List;
+import java.util.ArrayList;
+
+
+public class StackTest {
+    
+    public static void main(String[] args) {
+	IStack<Integer> intStack = new Stack<>();
+
+	intStack.push(4);
+	intStack.push(5);
+	intStack.push(9);
+
+	System.out.println(intStack.pop());
+	System.out.println(intStack.size());
+	System.out.println(intStack.peek());
+    }
+
+}
+
+
+interface IStack<T> {
+   /*
+    * 'pop' removed the last element from the stack and returns it
+    */
+    T pop();
+
+   /*
+    * 'push' adds an element to at the end of the stack and returns the new size
+    */
+    int push(T element);
+
+   /*
+    * 'size' returns the length of the stack
+    */
+    int size();
+
+   /*
+    * 'peek' returns the first element of the stack
+    */
+    T peek();
+}
+
+
+public class Stack<T> implements IStack<T> {
+    
+    private List<T> list;
+
+    public Stack() {
+	this.list = new ArrayList<>();
+    }
+
+    public T pop() {
+	return this.list.remove(this.size() - 1);
+    }
+
+    public int push(T element) {
+	this.list.add(element);
+	return this.size();
+    }
+
+    public int size() {
+	return this.list.size();
+    }
+
+    public T peek() {
+	return this.list.get(this.size() - 1);
+    }
+
+}
+
+