iterator
Class pnodePQ

java.lang.Object
  iterator.pnodePQ

Direct Known Subclasses:

pnodeSplayPQ

public abstract class pnodePQ

extends java.lang.Object

Implements a sorted binary tree. abstract methods enq and deq are used to add or remove elements from the tree.

Constructor Summary

pnodePQ()
class constructor, set count to 0.

Method Summary

abstract pnode	deq() removes the minimum (Ascending) or maximum (Descending) element from the tree.
boolean	empty() tests whether the tree is empty
abstract void	enq(pnode item) insert an element in the tree in the correct order.
int	length() returns the number of elements in the tree.
int	pnodeCMP(pnode a, pnode b) compares two elements.
boolean	pnodeEQ(pnode a, pnode b) tests whether the two elements are equal.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

pnodePQ

public pnodePQ()

class constructor, set count to 0.

Method Detail

length

public int length()

returns the number of elements in the tree.

Returns:

number of elements in the tree.

empty

public boolean empty()

tests whether the tree is empty

Returns:

true if tree is empty, false otherwise

enq

public abstract void enq(pnode item)
                  throws java.io.IOException,
                         UnknowAttrType,
                         TupleUtilsException

insert an element in the tree in the correct order.

Parameters:

item - the element to be inserted

Throws:

java.io.IOException - from lower layers

UnknowAttrType - attrSymbol or attrNull encountered

TupleUtilsException - error in tuple compare routines

deq

public abstract pnode deq()

removes the minimum (Ascending) or maximum (Descending) element from the tree.

Returns:

the element removed, null if the tree is empty

pnodeCMP

public int pnodeCMP(pnode a,
                    pnode b)
             throws java.io.IOException,
                    UnknowAttrType,
                    TupleUtilsException

compares two elements.

Parameters:

a - one of the element for comparison

b - the other element for comparison

Returns:

0 if the two are equal, 1 if a is greater, -1 if b is greater

Throws:

java.io.IOException - from lower layers

UnknowAttrType - attrSymbol or attrNull encountered

TupleUtilsException - error in tuple compare routines

pnodeEQ

public boolean pnodeEQ(pnode a,
                       pnode b)
                throws java.io.IOException,
                       UnknowAttrType,
                       TupleUtilsException

tests whether the two elements are equal.

Parameters:

a - one of the element for comparison

b - the other element for comparison

Returns:

true if a == b, false otherwise

Throws:

java.io.IOException - from lower layers

UnknowAttrType - attrSymbol or attrNull encountered

TupleUtilsException - error in tuple compare routines