operators
Class PSClear

java.lang.Object
  operators.PSClear

All Implemented Interfaces:

PSObject, PSOperator, PSStackOperator

public class PSClear

extends java.lang.Object

implements PSStackOperator

Implements PSStackOperator interface.

Methods such as getOperatorToken() are inherited by PSStackOperator interface which in turn, are inherited by PSOperator.This concrete class is responsible for the removal of the elements found in stack.

Constructor Summary

PSClear()

Method Summary

void	action(PSStack s) Clears the stack from it's contents.
java.lang.String	getOperatorToken() Returns the token identifying this operator.
boolean	isValid(PSStack s) Checks if it valid to use this operator now.

Methods inherited from class java.lang.Object

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

Constructor Detail

PSClear

public PSClear()

Method Detail

getOperatorToken

public java.lang.String getOperatorToken()

Returns the token identifying this operator.

Returns the name of the operand that this concrete class simulates,here "clear".

Precondition : A valid operator class has been created.
Postcondition : A string is returned,labeling the semantics of this class.

Specified by:

getOperatorToken in interface PSOperator

Returns:

The token identifying this operator.

isValid

public boolean isValid(PSStack s)
                throws PSSyntaxException

Checks if it valid to use this operator now.

The removal can occur only if the stack contains elements.

Precondition : A valid instance of PSStack is given.
Postcondition : A reply to whether an element of the stack can be copied on top of the stack.

Specified by:

isValid in interface PSOperator

Parameters:

s - A reference to a PSStack instance.

Returns:

True if the operation can be performed,false otherwise.

Throws:

PSSyntaxException - The syntax of the token is wrong.

action

public void action(PSStack s)

Clears the stack from it's contents.

Removes all the elements from stack.

Precondition : A valid stack is given to method.
Postcondition : An element will be copied on top the stack

Specified by:

action in interface PSStackOperator

Parameters:

s - The Run-time Stack which is needed.