Data commit

Task/Stack/Java/stack-1.java

@@ -0,0 +1,21 @@
+import java.util.Stack;
+
+public class StackTest {
+    public static void main( final String[] args ) {
+        final Stack<String> stack = new Stack<String>();
+
+        System.out.println( "New stack empty? " + stack.empty() );
+
+        stack.push( "There can be only one" );
+        System.out.println( "Pushed stack empty? " + stack.empty() );
+        System.out.println( "Popped single entry: " + stack.pop() );
+
+        stack.push( "First" );
+        stack.push( "Second" );
+        System.out.println( "Popped entry should be second: " + stack.pop() );
+
+        // Popping an empty stack will throw...
+        stack.pop();
+        stack.pop();
+    }
+}

Task/Stack/Java/stack-2.java

@@ -0,0 +1,29 @@
+public class Stack{
+    private Node first = null;
+    public boolean isEmpty(){
+        return first == null;
+    }
+    public Object Pop(){
+        if(isEmpty())
+            throw new Exception("Can't Pop from an empty Stack.");
+        else{
+            Object temp = first.value;
+            first = first.next;
+            return temp;
+        }
+    }
+    public void Push(Object o){
+        first = new Node(o, first);
+    }
+    class Node{
+        public Node next;
+        public Object value;
+        public Node(Object value){
+            this(value, null);
+        }
+        public Node(Object value, Node next){
+            this.next = next;
+            this.value = value;
+        }
+    }
+}

Task/Stack/Java/stack-3.java

@@ -0,0 +1,29 @@
+public class Stack<T>{
+    private Node first = null;
+    public boolean isEmpty(){
+        return first == null;
+    }
+    public T Pop(){
+        if(isEmpty())
+            throw new Exception("Can't Pop from an empty Stack.");
+        else{
+            T temp = first.value;
+            first = first.next;
+            return temp;
+        }
+    }
+    public void Push(T o){
+        first = new Node(o, first);
+    }
+    class Node{
+        public Node next;
+        public T value;
+        public Node(T value){
+            this(value, null);
+        }
+        public Node(T value, Node next){
+            this.next = next;
+            this.value = value;
+        }
+    }
+}