a simple queue

				
//**************************************
// Name: a simple queue
// Description:it's a simple queue written by me with generics 
it's for beginner to understand how a queue works
for an integer QUEUE:
( Queue<Integer> myQueue = new Queue<Integer>() )
// By: felix knorr
//
// Inputs:/
//
// Returns:/
//
// Side Effects:/
//
//This code is copyrighted and has// limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=6350&lngWId=2//for details.//**************************************

public class Queue<T> {
	private Object[] arr;
	private int 	 getIndex;
	private int putIndex;
	private int size;
	private int usedSize;
	private boolean isSetSize;
	
	public Queue(){
		this(10);
		isSetSize = true;
	}
	
	public Queue(int size){
		arr= new Object[size];
		getIndex = 0;
		putIndex = 0;
		this.size = size;
		usedSize = 0;
	}
	
	public boolean isEmpty(){
		return usedSize == 0;
	}
	
	@SuppressWarnings("unchecked")
	public T get() throws QueueUnderflowExeption{
		usedSize--;
		
		if(usedSize == 0)
			throw new QueueUnderflowExeption("Die Queue ist leer");
		
		T element = (T)arr[getIndex];
		getIndex = (getIndex+1)%size;
		return element;
	}
	public void put(T element) throws QueueOverflowExeption{
		usedSize++;
		
		if((usedSize >= size) && (isSetSize))
			extend();
		else if(usedSize >= size)
			throw new QueueOverflowExeption("Die Queue ist voll");
			
		arr[putIndex] = element;
		putIndex = (putIndex+1)%size;
	}
	
	public int getSize() {
		return size;
	}
	public int getUsedSize() {
		return usedSize;
	}
	public boolean isSetSize() {
		return isSetSize;
	}
	public String toString(){
		StringBuilder sb = new StringBuilder();
		
		for(int i=usedSize;i>0;i--){
			T element;
			try {
				element = this.get();
				sb.append(element.toString());
				sb.append("\n");
				this.put(element);
			} catch (QueueUnderflowExeption e) {
				System.out.println(e.getMessage());
			} catch (QueueOverflowExeption e) {
				System.out.println(e.getMessage());
			}
			
		}
		return sb.toString();
	}
	
	private void extend() {
		Object[] tempArr = new Object[size*2];
		int count = 0;
		
		while(putIndex != getIndex){
			try {
				tempArr[count] = get();
				count++;
			} catch (QueueUnderflowExeption e) {
				e.printStackTrace();
			}
		}
		usedSize = count+1;
		getIndex = 0;
		putIndex = count;
		size *= 2;
		arr = tempArr;
	}
	public static void main(String[] args){
		Queue<String> myQueue = new Queue<String>();
		
		for(int i=0;i<20; i++){
			try {
				myQueue.put(i+"");
			} catch (QueueOverflowExeption e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		System.out.println(myQueue.toString());
		try {
			myQueue.get();
			myQueue.get();
			myQueue.get();
		} catch (QueueUnderflowExeption e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		System.out.println(myQueue.toString());
	}
}
//
//_ _ _ _ _ _ _ _ _ _
//	|_|_|_|_|_|_|_|_|_|_|
// ^ ^
///_\/_\
//	| |
// putIndex getIndex
//
//
//____________________
//	|Queue| 
// |--------------------|
// |-arr:Object[]|
// |-putIndex:int|
// |-getIndex:int|
// |-size:int|
// |-usedSize:int|
// |-isSetSize:boolean |
// |--------------------|
// |+Queue()|
// |+Queue(int) |
// |+isEmpty():boolean |
// |+get():<T> |
// |+put(<T>)|
// |+getSize():int |
// |+getUsedSize:int|
// |+isSetSize():boolean|
// |+toString():String |
// |-extend()|
// |____________________|
public class QueueOverflowExeption extends Exception{
	private static final long serialVersionUID = 1L;
	public QueueOverflowExeption() { }			
	 
	public QueueOverflowExeption(String s){
		super(s);	
	}
}
public class QueueUnderflowExeption extends Exception{
	private static final long serialVersionUID = 1L;
	public QueueUnderflowExeption() { }			
	 
	 public QueueUnderflowExeption(String s){
	super(s);	
	 }
}