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/*
* SymbolTable.java
*
* Created on November 19, 2001
*/
package com.sun.jdo.spi.persistence.support.ejb.ejbqlc;
import java.util.Map;
import java.util.HashMap;
/**
* The symbol table handling declared identifies.
*
* @author Michael Bouschen
*/
public class SymbolTable
{
/**
* The table of declared identifier (symbols).
*/
protected Map symbols = new HashMap();
/**
* This method adds the specified identifier to this SymbolTable.
* The specified decl object provides details anbout the declaration.
* If this SymbolTable already defines an identifier with the same name,
* the SymbolTable is not changed and the existing declaration is returned.
* Otherwise <code>null</code> is returned.
* @param ident identifier to be declared
* @param decl new definition of identifier
* @return the old definition if the identifier was already declared;
* <code>null</code> otherwise
*/
public Object declare(String ident, Object decl)
{
Object old = symbols.get(ident);
if (old == null) {
symbols.put(ident.toUpperCase(), decl);
}
return old;
}
/**
* Checks whether the specified identifier is declared.
* @param ident the name of identifier to be tested
* @return <code>true</code> if the identifier is declared;
* <code>false</code> otherwise.
*/
public boolean isDeclared(String ident)
{
return (getDeclaration(ident) != null);
}
/**
* Checks the symbol table for the actual declaration of the specified
* identifier. The method returns the declaration object if available or
* <code>null</code> for an undeclared identifier.
* @param ident the name of identifier
* @return the declaration object if ident is declared;
* <code>null</code> otherise.
*/
public Object getDeclaration(String ident)
{
return symbols.get(ident.toUpperCase());
}
}