Added an implementation for a stack/queue in Java.

KTOmega · KTOmega · commit 47fe0bd2fff2 · 2016-10-11T01:21:08.000-07:00
Because @joyhsu0504 would probably find this helpful. - Added Java .class files to .gitignore. - Added Stack and related tests. - Added Queue and related tests.
diff --git a/.gitignore b/.gitignore
@@ -1 +1,2 @@
 *.o
+*.class
diff --git a/java/Queue/Queue.java b/java/Queue/Queue.java
@@ -0,0 +1,43 @@
+import java.util.ArrayList;
+
+class EmptyQueueException extends IndexOutOfBoundsException {
+	public EmptyQueueException() {
+		super("Queue is empty.");
+	}
+}
+
+class Queue<T> {
+	private ArrayList<T> list;
+	
+	public Queue() {
+		this.list = new ArrayList<T>();
+	}
+	
+	public void enqueue(T item) {
+		this.list.add(item);
+	}
+	
+	public T dequeue() {
+		if (this.size() == 0) {
+			throw new EmptyQueueException();
+		}
+		
+		return this.list.remove(0);
+	}
+	
+	public T peek() {
+		if (this.size() == 0) {
+			throw new EmptyQueueException();
+		}
+		
+		return this.list.get(0);
+	}
+	
+	public boolean isEmpty() {
+		return this.size() == 0;
+	}
+	
+	public int size() {
+		return this.list.size();
+	}
+}
diff --git a/java/Queue/QueueTester.java b/java/Queue/QueueTester.java
@@ -0,0 +1,32 @@
+class QueueTester {
+	public static void main(String[] args) {
+		Queue<Integer> queue = new Queue<Integer>();
+		
+		for (int i = 5; i >= 0; i--) {
+			queue.enqueue(i);
+			System.out.println("Enqueued " + i);
+		}
+		
+		System.out.println("Size: " + queue.size());
+		System.out.println("Top: " + queue.peek());
+		
+		while (queue.size() > 0) {
+			System.out.println(queue.dequeue());
+		}
+		
+		System.out.println("Size: " + queue.size());
+		System.out.print("Top: ");
+		
+		try {
+			System.out.println(queue.peek());
+		} catch (EmptyQueueException e) {
+			System.out.println(e.toString());
+		}
+		
+		try {
+			System.out.println(queue.dequeue());
+		} catch (EmptyQueueException e) {
+			System.out.println(e.toString());
+		}
+	}
+}
diff --git a/java/Stack/Stack.java b/java/Stack/Stack.java
@@ -0,0 +1,43 @@
+import java.util.ArrayList;
+
+class EmptyStackException extends IndexOutOfBoundsException {
+	public EmptyStackException() {
+		super("Stack is empty.");
+	}
+}
+
+class Stack<T> {
+	private ArrayList<T> list;
+	
+	public Stack() {
+		this.list = new ArrayList<T>();
+	}
+	
+	public void push(T item) {
+		this.list.add(item);
+	}
+	
+	public T pop() {
+		if (this.size() == 0) {
+			throw new EmptyStackException();
+		}
+		
+		return this.list.remove(this.size() - 1);
+	}
+	
+	public T peek() {
+		if (this.size() == 0) {
+			throw new EmptyStackException();
+		}
+		
+		return this.list.get(0);
+	}
+	
+	public boolean isEmpty() {
+		return this.size() == 0;
+	}
+	
+	public int size() {
+		return this.list.size();
+	}
+}
diff --git a/java/Stack/StackTester.java b/java/Stack/StackTester.java
@@ -0,0 +1,32 @@
+class StackTester {
+	public static void main(String[] args) {
+		Stack<Integer> stack = new Stack<Integer>();
+		
+		for (int i = 5; i >= 0; i--) {
+			stack.push(i);
+			System.out.println("Pushed " + i);
+		}
+		
+		System.out.println("Size: " + stack.size());
+		System.out.println("Top: " + stack.peek());
+		
+		while (stack.size() > 0) {
+			System.out.println(stack.pop());
+		}
+		
+		System.out.println("Size: " + stack.size());
+		System.out.print("Top: ");
+		
+		try {
+			System.out.println(stack.peek());
+		} catch (EmptyStackException e) {
+			System.out.println(e.toString());
+		}
+		
+		try {
+			System.out.println(stack.pop());
+		} catch (EmptyStackException e) {
+			System.out.println(e.toString());
+		}
+	}
+}
