Implement Queue in java
Program
import java.util.Queue;//interface where objects cant be created
import java.util.PriorityQueue;//PriorityQueue class provides the
facility of implementing queue operations but it orders the elements in the queue
import java.util.Scanner;//Scanner class reads data from the input
stream
class Queuedemo
{
public static void
main(String[] args)
{
int size=5;
Queue<Integer>
obj=new PriorityQueue<Integer>();
Scanner s=new
Scanner(System.in);
while(true)
{
System.out.println("1.Insert");
System.out.println("2.Delete");
System.out.println("3.Display");
System.out.println("4.Quit");
System.out.println("Enter choice");
int choice=s.nextInt();
switch(choice)
{
case 1:System.out.println("Enter
the element to be inserted into queue");
int
e=s.nextInt();
if(obj.size()==size)
System.out.println("Queue overflow");
else
obj.add(e);//inserts element into queue
break;
case
2:if(obj.isEmpty())//checks whether queue is empty or not
System.out.println("Queue underflow");
else
System.out.println("Element deleted from queue"+obj.remove());
break;
case 3:if(obj.isEmpty())
System.out.println("Queue is empty");
else
{
System.out.println("Queue elements");
for(Integer
x:obj)//using enhanced for loop or forEach loop
System.out.println(x);
}
break;
case 4:System.exit(0);
default:System.out.println("Wrong choice");
}
}
}
}
Expected Output
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
10
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
20
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
30
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
40
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
50
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
60
Queue overflow
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
3
Queue elements
10
20
30
40
50
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue10
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue20
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue30
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue40
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
1
Enter the element to be inserted into queue
60
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
3
Queue elements
50
60
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue50
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Element deleted from queue60
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
2
Queue underflow
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
3
Queue is empty
1.Insert
2.Delete
3.Display
4.Quit
Enter choice
4
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