Java Reference
In-Depth Information
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Array-basedqueueimplementation
*
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classAQueue<E>implementsQueue<E>{
privatestaticfinalintdefaultSize=10;
privateintmaxSize; //Maximumsizeofqueue
privateintfront; //Indexoffrontelement
privateintrear; //Indexofrearelement
privateE[]listArray; //Arrayholdingqueueelements
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Constructors
*
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AQueue(){this(defaultSize);}
@SuppressWarnings("unchecked")//Forgenericarray
AQueue(intsize){
maxSize=size+1; //Oneextraspaceisallocated
rear=0;front=1;
listArray=(E[])newObject[maxSize];//CreatelistArray
}
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Reinitialize
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publicvoidclear()
{rear=0;front=1;}
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Put"it"inqueue
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publicvoidenqueue(Eit){
assert((rear+2)%maxSize)!=front:"Queueisfull";
rear=(rear+1)%maxSize;//Circularincrement
listArray[rear]=it;
}
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Removeandreturnfrontvalue
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publicEdequeue(){
assertlength()!=0:"Queueisempty";
Eit=listArray[front];
front=(front+1)%maxSize;//Circularincrement
returnit;
}
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@returnFrontvalue
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publicEfrontValue(){
assertlength()!=0:"Queueisempty";
returnlistArray[front];
}
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@returnQueuesize
*
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publicintlength()
{return((rear+maxSize)-front+1)%maxSize;}
Figure4.27
An array-based queue implementation.
