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Queue.java
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Queue.java
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public class Queue {
private static final int SIZE = 4;
private Node[] nodes = new Node[SIZE];
private int headIndex = -1;
private int tailIndex = -1;
public int currentSize = 0;
public static final class Node{
private String key;
private String value;
public Node(String key, String value){
this.key = key;
this.value = value;
}
public String toString(){
return "Key: "+ key +", Value "+ value;
}
}
public void enqueue(Node n) throws Exception{
if (isQueueFull()){
throw new Exception("Queue overflow!");
}
if (headIndex == -1 && tailIndex == -1){
headIndex = 0;
tailIndex = 0;
}
nodes[tailIndex] = n;
tailIndex = (tailIndex + 1) % SIZE;
currentSize++;
}
public Node dequeue() throws Exception {
if (isQueueEmpty()){
throw new Exception("Queue underflow!");
}
Node node = nodes[headIndex];
nodes[headIndex] = null;
headIndex = (headIndex + 1) % SIZE;
if (headIndex == tailIndex){
headIndex = 0;
tailIndex = 0;
}
currentSize--;
return node;
}
public boolean isQueueFull(){
return currentSize == SIZE;
}
public boolean isQueueEmpty(){
return currentSize == 0;
}
public static void main (String[] args) throws Exception{
Queue q = new Queue();
q.enqueue(new Node("a", "b"));
q.enqueue(new Node("d", "e"));
q.enqueue(new Node("f", "e"));
q.enqueue(new Node("h", "e"));
System.out.println(q.dequeue());
q.enqueue(new Node("h1", "e"));
System.out.println(q.dequeue());
System.out.println(q.dequeue());
System.out.println(q.dequeue());
q.enqueue(new Node("g", "e"));
System.out.println(q.dequeue());
System.out.println(q.dequeue());
}
}