class JollyQ2 implements Queue  // save as JollyQ2.java
  {
    private int [] storage;
    private int front, back, length, size;
    static final int DEFAULT_SIZE = 1000;

    public JollyQ2(int m)
      {
        size = m;
        storage = new int[size];
        front = back = 0;
        length = 0;
      }
    public JollyQ2()
      {
        this( DEFAULT_SIZE );
      }

    public void enterQ( int a )
      { if ( !isQFull() ) {storage[back] = a; back++; length++;}
        else              System.out.println("Awfully sorry, but we're full"); 
      }
    public int leaveQ()
      { if (!isQEmpty() )
          { int temp = storage[front]; front++; length--; return temp; }
        else             
          { System.out.println("Awfully sorry, but we're empty");
            return 0.0; // this is not ideal, should handle this error state better
          }
      }
    public int peekAtQ(){ return storage[front]; }
    public int qLength(){ return length; }
    public boolean isQEmpty(){ return (length == 0); }
    public boolean isQFull(){ return (length == size); }
    public int qCapacity(){ return size; } // total capacity
  }  // this is a linear array implementation of a queue


+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

class JollyQ3 implements Queue  // save as JollyQ3.java
  {
    private int [] storage;
    private int front, back, length, size;
    static final int DEFAULT_SIZE = 1000;

    public JollyQ3(int m)
      {
        size = m;
        storage = new int[size];
        front = back = 0;
        length = 0;
      }
    public JollyQ3()
      {
        this( DEFAULT_SIZE );
      }

    public void enterQ( int a )
      { if ( !isQFull() ) {storage[back] = a;  back = (++back)%size; length++;}
        else              System.out.println("Awfully sorry, but we're full"); 
      }
    public int leaveQ()
      { if (!isQEmpty() ) 
          { int temp = storage[front]; 
            front = (++front) % size; 
            length--; 
            return temp;
          }
        else
          { System.out.println("Awfully sorry, but we're empty");
            return 0; // this is not ideal for an error condition
                      // should really have some exception handling here
          }
      }
    public int peekAtQ(){ return storage[front]; }
    public int qLength(){ return length; }
    public boolean isQEmpty(){ return (length == 0); }
    public boolean isQFull(){ return (length == size); }
    public int qCapacity(){ return size; } // total capacity
  } // this implements a circular array version of a queue

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

public class QThingy   // save as QThingy.java 
  {
    private int value;
    private QThingy next;

    public QThingy(int value, QThingy next)
      { setValue(value); setQThingy(next); }
    public QThingy(int value)
      { this(value, null); }
    public QThingy()
      { this(0); }

    public void setValue(int value)
      { this.value = value; }
    public int getValue()
      { return this.value; }
    public void setNext(Qthingy next)
      { this.next = next; }
    public QThingy getNext()
      { return this.next; }
  } 

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

class JollyQ4 implements Queue
  {
    private QThingy header, front, back;
    private int length; 
    static final int DEFAULT_SIZE = 0;

    public JollyQ4(int m)  // this int m is quite vacuous!!!
      {
        header = new QThingy(); 
        back = header;  
        length = 0;
      }
    public JollyQ4()
      {
        this( DEFAULT_SIZE );
      }

    public void enterQ( int a )
      { 
        QThingy tempQThingy = new QThingy( a );
        back.setNext(tempQThingy); 
        back = tempQThingy;
        if ( isQEmpty() ) front = back;
        length++;
      }

    public int leaveQ()
      { if (!isQEmpty() ) 
          { int tempValue = front.getValue();
            front = front.getNext();
            length--;
            return tempValue;
          }
        else
          { System.out.println("Awfully sorry, but we're empty");
            return 0; // this is not ideal for an error condition
                      // should really have some exception handling here
          }
      }
    public int peekAtQ()
      { if ( !isQEmpty() ) return front.getValue(); 
        return 0; // this is not ideal for an error condition
                  // should really have some exception handling here}
    public int qLength(){ return length; }
    public boolean isQEmpty(){ return (length == 0); }
    public boolean isQFull(){ return false; }
    public int qCapacity(){ return Integer.MAX_VALUE; } // total capacity
  } // this implements a non-array version of a queue

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++