最小关键字值的数据项总是在数组的高端（最高下标值处），而且最大的数据项总是在下标值为0的位置上。
// priorityQ.java
// demonstrates priority queue
// to run this program: C>java PriorityQApp
////////////////////////////////////////////////////////////////
class PriorityQ
{
// array in sorted order, from max at 0 to min at size-1
private int maxSize;
private long[] queArray;
private int nItems;
//-------------------------------------------------------------
public PriorityQ(int s) // constructor
{
maxSize = s;
queArray = new long[maxSize];
nItems = 0;
}
//-------------------------------------------------------------
public void insert(long item) // insert item
{
int j;
if(nItems==0) // if no items,
queArray[nItems++] = item; // insert at 0
else // if items,
{
for(j=nItems-1; j>=0; j--) // start at end,
{
if( item > queArray[j] ) // if new item larger,
queArray[j+1] = queArray[j]; // shift upward
else // if smaller,
break; // done shifting
} // end for
queArray[j+1] = item; // insert it
nItems++;
} // end else (nItems > 0)
} // end insert()
//-------------------------------------------------------------
public long remove() // remove minimum item
{ return queArray[--nItems]; }
//-------------------------------------------------------------
public long peekMin() // peek at minimum item
{ return queArray[nItems-1]; }
//-------------------------------------------------------------
public boolean isEmpty() // true if queue is empty
{ return (nItems==0); }
//-------------------------------------------------------------
public boolean isFull() // true if queue is full
{ return (nItems == maxSize); }
//-------------------------------------------------------------
} // end class PriorityQ
////////////////////////////////////////////////////////////////
class PriorityQApp
{
public static void main(String[] args)
{
PriorityQ thePQ = new PriorityQ(5);
thePQ.insert(30);
thePQ.insert(50);
thePQ.insert(10);
thePQ.insert(40);
thePQ.insert(20);
while( !thePQ.isEmpty() )
{
long item = thePQ.remove();
System.out.print(item + " "); // 10, 20, 30, 40, 50
} // end while
System.out.println("");
} // end main()
//-------------------------------------------------------------
} // end class PriorityQApp
////////////////////////////////////////////////////////////////