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Data Structure/Queue/Basic Queue Expand file tree Collapse file tree Original file line number Diff line number Diff line change 1+ import java .util .Arrays ;
2+ import java .util .Scanner ;
3+ class QueUe {
4+
5+ int [] Qarray ;
6+ int size ;
7+ int front ,rear ;
8+
9+ QueUe (int capacity ){
10+ size =capacity ;
11+ Qarray = new int [capacity ];
12+ rear =-1 ;
13+ front =-1 ;
14+ }
15+
16+ void display (){
17+ System .out .println (Arrays .toString (Qarray ));
18+ }
19+
20+ void value (){
21+ System .out .println ("front:" +front +"\t rare:" +rear );
22+ }
23+
24+ void peek ()
25+ {
26+ if (isEmpty ())
27+ {
28+ System .out .println ("Queue empty!" );
29+ return ;
30+ }
31+ System .out .println ("peek value is " +Qarray [front ]);
32+ }
33+
34+ void enqueue (int val ){
35+ if (isFull ())
36+ {
37+ System .out .println ("queue is full!" );
38+ return ;
39+ }
40+ if (rear ==-1 ){
41+ front ++;
42+ }
43+ System .out .println ("Adding " + val );
44+
45+ rear ++ ;
46+ Qarray [rear ] = val ;
47+ }
48+
49+ void dequeue ()
50+ {
51+ // check for queue underflow
52+ if (isEmpty ())
53+ {
54+ System .out .println ("queue is empty" );
55+ return ;
56+ }
57+
58+ System .out .println ("Deleting " + Qarray [front ]);
59+ if (front ==rear ){
60+ front =-1 ;
61+ rear =-1 ;//last element
62+ return ;
63+ }
64+ front ++;
65+ }
66+
67+ Boolean isFull ()
68+ {
69+ return (rear ==size -1 );
70+ }
71+
72+ Boolean isEmpty ()
73+ {
74+ return (front ==-1 );
75+ }
76+ }
77+ class BasicQueue {
78+
79+ public static void main (String [] args )
80+ {
81+ QueUe que = new QueUe (4 );
82+
83+ que .enqueue (5 );
84+ que .peek ();
85+ que .dequeue ();
86+ que .peek ();
87+ que .enqueue (20 );
88+ que .peek ();
89+ que .enqueue (4 );
90+ que .value ();
91+ que .enqueue (17 );
92+ que .enqueue (9 );
93+
94+ if (que .isFull ())
95+ System .out .println ("Queue Is full" );
96+
97+ que .peek ();
98+ que .dequeue ();
99+ que .dequeue ();
100+ que .peek ();
101+
102+ System .out .println ("Queue size is " + que .size );
103+
104+ que .dequeue ();
105+ que .dequeue ();
106+
107+ if (que .isEmpty ())
108+ System .out .println ("Queue Is Empty" );
109+
110+ }
111+ }
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