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package bjc.pratt.tokens;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import bjc.utils.funcutils.StringUtils;
import bjc.utils.parserutils.ParserException;
/**
* A stream of tokens.
*
* @author EVE
*
* @param <K>
* The key type of the token.
*
* @param <V>
* The value type of the token.
*/
public abstract class TokenStream<K, V> implements Iterator<Token<K, V>> {
/**
* The exception thrown when an expectation fails.
*
* @author EVE
*
*/
public static class ExpectationException extends ParserException {
private static final long serialVersionUID = 4299299480127680805L;
/**
* Create a new exception with the specified message.
*
* @param msg
* The message of the exception.
*/
public ExpectationException(final String msg) {
super(msg);
}
}
/**
* Get the current token.
*
* @return The current token.
*/
public abstract Token<K, V> current();
@Override
public abstract Token<K, V> next();
@Override
public abstract boolean hasNext();
/**
* Utility method for checking that the next token is one of a specific
* set of types, and then consuming it.
*
* @param expectedKeys
* The expected values
*
* @throws ExpectationException
* If the token is not one of the expected types.
*/
public void expect(final Set<K> expectedKeys) throws ExpectationException {
final K curKey = current().getKey();
if (!expectedKeys.contains(curKey)) {
final String expectedList = StringUtils.toEnglishList(expectedKeys.toArray(), false);
throw new ExpectationException("One of '" + expectedList + "' was expected, not " + curKey);
}
next();
}
/**
* Utility method for checking that the next token is one of a specific
* set of types, and then consuming it.
*
* @param expectedKeys
* The expected values
*
* @throws ExpectationException
* If the token is not one of the expected types.
*/
@SafeVarargs
public final void expect(final K... expectedKeys) throws ExpectationException {
expect(new HashSet<>(Arrays.asList(expectedKeys)));
}
/**
* Check whether the head token is a certain type.
*
* @param val
* The type to check for.
*
* @return Whether or not the head token is of that type.
*/
public boolean headIs(final K val) {
return current().getKey().equals(val);
}
}
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