/**
*
* @author Adeniran Adetunji
*/
public class ArrayStaticQueue {
//Declaring the instance variables of a queue. Initalizing head and tail to zero
int headRef=0;
int tailRef=0;
char [] arrayQueue;
//Method to create queue array
void initializeQueue(int Size)
{
arrayQueue = new char[Size];
for( int i=0; i<arrayQueue.length; i++)
{
arrayQueue[i] = '\u0000';
}
}
//This method checks if queue is empty
boolean isEmpty()
{
boolean test= true;
for (int i=0; i<arrayQueue.length; i++)
{
if(arrayQueue[i]!='\u0000')
test=false;
}
return test;
}
//This method test if queue is full
boolean isFull()
{
boolean test = true;
for (int i=0; i<arrayQueue.length; i++)
{
if(arrayQueue[i]=='\u0000')
test = false;
}
return test;
}
//This method adds item to queue
void addItem( char c)
{
// The test determines if the queue is full
boolean test=isFull();
// If the queue is full
if(test)
{
//The system should print QUEUE IS FULL
System.out.println("Queue is Full");
}
else
{
arrayQueue[tailRef]=c;
}
setTail();
}
//This method set new tail location after adding item to queue
void setTail()
{
//Test if queue is full
boolean test=isFull();
//if is full
if(test)
{
//Then tail index becomes -1
tailRef=-1;
}
//If queue is not full
else
{
//Get the current tail index in nTail variable
int nTail = tailRef;
//Check for free space to the right-side of the tail
for(int i=tailRef; tailRef<arrayQueue.length; i++)
{
//if found...
if(arrayQueue[i]=='\u0000')
{
//set new tail at the index of the free space
tailRef=i;
//break out of the loop
break;
}
}
//Test if tailRef is not updated by the loop above
//If test is true: that is loop is not updated
if (nTail==tailRef)
{
//start searching for the free space from the begining of the
//queue i.e. from index 0
for (int k=0; k<arrayQueue.length; k++)
{
//Get first free space
if(arrayQueue[k]=='\u0000')
{
//Update tailRef at the index of the first free space gotten
tailRef=k;
//break out of the loop
break;
}
}
}
}
}
//This method removes item from queue
void removeItem()
{
boolean test = isEmpty();
if(test)
{
System.out.print("Queue is empty");
}
else
{
arrayQueue[headRef]='\u0000';
if(tailRef==-1)
{
tailRef=headRef;
}
}
setHead();
}
//This method set new head location after removing item from queue
void setHead()
{
boolean test = isEmpty();
if(test)
{
headRef=0;
}
else
{
if(headRef+1<arrayQueue.length)
{
headRef=headRef+1;
}
else
{
for(int i=0; i<arrayQueue.length; i++)
{
if(arrayQueue[i]!='\u0000')
headRef=i;
break;
}
}
}
}
}
....Class Instance...
package queuedatastructure;
/**
*
* @author Adeniran Adetunji
*/
public class QueueDataStructure {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
ArrayStaticQueue myQueue = new ArrayStaticQueue();
myQueue.initializeQueue(5); //Initializes queue that can hold five characters
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*2*/ boolean check = myQueue.isEmpty();
System.out.println(check);
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
/*4*/ myQueue.addItem('A');
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*2*/ check = myQueue.isEmpty();
System.out.println(check);
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
/*5*/ myQueue.addItem('B');
myQueue.addItem('C');
myQueue.addItem('D');
myQueue.addItem('E');
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*2*/ check = myQueue.isEmpty();
System.out.println(check);
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
check=myQueue.isFull();
/*6*/ System.out.println(check);
/*7*/ myQueue.addItem('F');
/*8*/ myQueue.removeItem();
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
/*9*/ myQueue.removeItem();
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
/*10*/ myQueue.removeItem();
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
/*11*/ myQueue.addItem('F');
/*12*/ myQueue.removeItem();
/*1.*/ for (int i = 0; i<myQueue.arrayQueue.length; i++)
{
System.out.println(myQueue.arrayQueue[i]);
}
/*3*/ System.out.println("Head =" + myQueue.headRef);
System.out.println("Tail =" + myQueue.tailRef);
}
}
Output
run:
1.
2. true
3. Head =0
Tail =0
4.A
1. false
2. Head =0
3. Tail =1
//After adding item at /*5*/
1.A
B
C
D
E
2.false
3.Head =0
4.Tail =-1
6.True
7.Queue is Full
//After /*8*/
1.
B
C
D
E
3.Head =1
4.Tail =0
//After /*9*/
C
D
E
Head =2
Tail =0
//After /*10*/
1.
D
E
3.Head =3
4.Tail =0
//After /*11*/ & /*12*/
F
E
Head =4
Tail =1
BUILD SUCCESSFUL (total time: 9 seconds)
F
E
Head =4
Tail =1
BUILD SUCCESSFUL (total time: 9 seconds)
