Thread: Using Queue, cannot find symbol method enqueue

Hello, I have taken only some programming and am just beginning to really learn some little more advanced Java. When I was programming this I took some code I was supplied with and modified it.

The only problem I am really having is that I cannot figure out why my enqueue() method won't accept string arrays and why the NewArray() method is not found. Can anybody help me?

Here is my code:

ListQueue.java

// ListQueue class
//
// CONSTRUCTION: with no initializer
//
// ******************PUBLIC OPERATIONS*********************
// void enqueue( x ) --> Insert x
// String[] getFront( ) --> Return least recently inserted item
// String[] dequeue( ) --> Return and remove least recent item
// boolean isEmpty( ) --> Return true if empty; else false
// void makeEmpty( ) --> Remove all items
// ******************ERRORS************************** ******
// getFront or dequeue on empty queue

/**
* List-based implementation of the queue.
*/

import java.util.Arrays;
import java.io.*;
import java.util.Scanner;
import java.lang.Object;

public class ListQueue implements QueueInterface{

/**
* Construct the queue.
*/
public ListQueue( ) {
front = back = null;
}

/**
* Test if the queue is logically empty.
* @return true if empty, false otherwise.
*/
public boolean isEmpty( ) {
return front == null;
}

/**
* Insert a new item into the queue.
* @param x the item to insert.
*/
public void Enqueue( String[] x ) {
if( isEmpty( ) ) // Make queue of one element
back = front = new ListNode( x );
else // Regular case
back = back.next = new ListNode( x );
}

/**
* Return and remove the least recently inserted item
* from the queue.
* @return the least recently inserted item in the queue.
* @throws UnderflowException if the queue is empty.
*/
public String[] dequeue( ) {
if( isEmpty( ) )
throw new UnderflowException( "ListQueue dequeue" );

String[] returnValue = front.element;
front = front.next;
return returnValue;
}

/**
* Get the least recently inserted item in the queue.
* Does not alter the queue.
* @return the least recently inserted item in the queue.
* @throws UnderflowException if the queue is empty.
*/
public String[] getFront( ) {
if( isEmpty( ) )
throw new UnderflowException( "ListQueue getFront" );
return front.element;
}

/**
* Make the queue logically empty.
*/
public void makeEmpty( ) {
front = null;
back = null;
}



private ListNode front;
private ListNode back;

//New stuff
class NewArray{

String [] arr;

public String [] NewArray() {
arr = new String [10];
fill();
return arr;
}

public void sort(){
Arrays.sort(arr);
}

public void fill(){
for(int i=0; i<=10; i++){
arr[i] = ReadThread(); // have program read words from file eventually
// arr[i] = names.next(); ?
}

}

public String ReadThread(){
String dummy = "missing";
try{
File numbersFile = new File("numbers.txt");
File namesFile = new File("names.txt");
Scanner numbers = new Scanner(numbersFile);
Scanner names = new Scanner(namesFile);
dummy = names.next();
}
catch(FileNotFoundException e){
System.out.println("Not Found");
}
return dummy;
}


}
}

/**
* Exception class for access in empty containers
* such as stacks, queues, and priority queues.
*/


class ListNode {
// Constructors
public ListNode( String[] theElement ) {
this( theElement, null );
}

public ListNode( String[] theElement, ListNode n ) {
element = theElement;
next = n;
}

public String[] element;
public ListNode next;
}


QueueInterface.java


// Queue interface
//
// ******************PUBLIC OPERATIONS*********************
// void enqueue( x ) --> Insert x
// Object getFront( ) --> Return least recently inserted item
// Object dequeue( ) --> Return and remove least recent item
// boolean isEmpty( ) --> Return true if empty; else false
// void makeEmpty( ) --> Remove all items
// ******************ERRORS************************** ******
// getFront or dequeue on empty queue

/**
* Protocol for queues.
* @author Mark Allen Weiss
*/
public interface QueueInterface {
/**
* Insert a new item into the queue.
* @param x the item to insert.
*/
void Enqueue( String[] x );

/**
* Get the least recently inserted item in the queue.
* Does not alter the queue.
* @return the least recently inserted item in the queue.
* @exception UnderflowException if the queue is empty.
*/
String[] getFront( );

/**
* Return and remove the least recently inserted item
* from the queue.
* @return the least recently inserted item in the queue.
* @exception UnderflowException if the queue is empty.
*/
String[] dequeue( );

/**
* Test if the queue is logically empty.
* @return true if empty, false otherwise.
*/
boolean isEmpty( );

/**
* Make the queue logically empty.
*/
void makeEmpty( );
}


TestQueue.java

import java.lang.Object;

public class TestQueue{

public static void main(String [] args){

//Add code here to start threads
String [] arrayname = new String [10];
ListQueue queue = new ListQueue();
Enqueue(arrayname);
arrayname = NewArray();
Enqueue(NewArray());
Enqueue(arrayname);

}
}

UnderflowException.java

public class UnderflowException extends RuntimeException {
/**
* Construct this exception object.
* @param message the error message.
*/
public UnderflowException( String message ) {
super( message );
}
}

hy my enqueue() method won't accept string arrays and why the NewArray() method is not found.

Do you get an error message ? Please copy and paste the full text here.

Please wrap your posted code in code tags to preserve its formatting. See: BB Code List - Java Forums

Java naming conventions: Class names begin with uppercase, methods and variables with lowercase

public String [] NewArray() {
vs
public String [] newArray() {

Originally Posted by Norm

Do you get an error message ? Please copy and paste the full text here.

Please wrap your posted code in code tags to preserve its formatting. See: BB Code List - Java Forums

Java naming conventions: Class names begin with uppercase, methods and variables with lowercase

public String [] NewArray() {
vs
public String [] newArray() {

Thank you, the problem that I found in my main was that I was not calling the instantiated object followed by the method.
example:
Object is of type Queue, named q1
Method is enqueue()

my code read:
enqueue(Something);

while it should have been:
q1.enqueue(Something);

Forgetting the created object caused the "cannot find symbol method" error, because enqueue belongs to Queue and not my main method.

Thanks anyways