operators
Class PSStr

java.lang.Object
  operators.PSStr

All Implemented Interfaces:

PSObject, PSOperator, PSStringOperator

public class PSStr

extends java.lang.Object

implements PSStringOperator

Implements PSStringOperator interface.

Methods such as getOperatorToken() are inherited from PSStringOperator interface which, in turn, are inherited from PSOperator. This concrete class is responsible for creating an string of size n containing null characters.

Constructor Summary

PSStr()

Method Summary

void	action(PSStack s) Creates the string.
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

PSStr

public PSStr()

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 "string".

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.

A string can be created if a size number is given.

Precondition : A valid instance of PSStack with a PSNumber on top.
Postcondition : A reply to the question whether the operator can perfom its defined behaviour.

Specified by:

isValid in interface PSOperator

Parameters:

s - A reference to PSStack instance.

Returns:

True if the operation can be executed, false otherwise.

Throws:

PSSyntaxException - The syntax of the token is wrong.

action

public void action(PSStack s)

Creates the string.

Precondition : A valid stack is given to method with a PSNumber on top.
Postcondition : A string will be created of the size given containing null chars and be pushed back in the stack.

Specified by:

action in interface PSStringOperator

Parameters:

s - The Runtime Stack which contains the size of the string and will hold the string.