Linked Data Structures - Java - page 802

Display 15.29 A Queue Class (part 2 of 2)

25 /**
26 Adds a String to the back of the queue.
27 */
28 public void addToBack(String itemName)
< The definition of this method is Self-Test Exercise 18. >

29 public boolean isEmpty( )

30 {

31 return (front == null );

32 }

33 public void clear( )

34 {

35 front = null ;

36 back = null ;

37 }

38 /**

39 Returns the String in the front of the queue.

40 Returns null if queue is empty.

41 */

42 public String whoIsNext( )

43 {

44 if (front == null )

45 return null ;

46 else

47 return front.item;

48 }

49
50 /**

51 Removes a String from the front of the queue.

52 Returns false if the list is empty.

53 */

54 public boolean removeFront( )

55 {

56 if (front != null )

57 {

58 front = front.link;

59 return true ;

60 }

61 else

62 return false ;

63 }

64 }