ECS140A-Project 1 Solved

For this project you will be writing several Java classes to implement a programming language scanner and a CSV parser. The classes developed in this project will be used in subsequent projects. A Token class has been provided for you and an interface the Scanner will rely on for input has also been provided. The Scanner class must take in a PeekableCharacterStream and a List of keywords and must produce a stream of Tokens that are queried from either peekNextToken or getNextToken methods. The rules for the tokens defined below. You will also develop the CSVParser class that will parse CSV files into Maps, one for each row.

Your first task is to develop a class that implements the PeekableCharacterStream interface for a FileInputStream.   

public interface PeekableCharacterStream{ 

    // Returns true if more characters are available, false otherwise     public boolean moreAvailable(); 

 

    // Returns the next character that would be returned without consuming  

    // the character. If no more characters are available -1 is returned.     public int peekNextChar(); 

 

    // Returns the character ahead in the stream without consuming the 

    // the character. peekAheadChar(0) returns the same character as  

    // peekNextChar(). If no more characters are available at that position  

    // -1 is returned.     public int peekAheadChar(int ahead); 

 

    // Returns the next character and consumes it. If no more characters are  

    // available -1 is returned.     public int getNextChar(); 

 

    // Closes the stream.     public void close(); } 

Your second task is to develop the Scanner class that will rely on the PeekableCharacterStream interface and the Token class. The Scanner must have the following minimal interface.

public class Scanner{ 

    // Constructor that takes in a stream and a list of keywords. 

    public Scanner(PeekableCharacterStream stream, List<String keywordlist);  

    // Returns the next token without consuming it. If no more tokens are  

    // available a None token is returned. 

    public Token peekNextToken(); 

 

    // Returns the next token and consumes it. If no more tokens are  

    // available a None token is returned. 

    public Token getNextToken(); 

} 

Token Rules: 

Identifier := ( _ | Alpha ) { ( _ | Digit | Alpha )  } 

Operator := ( | , | ) | { | } | = | == | < | | <= | = | != | + | - | * |  

            / | ;    

IntConstant := [ - ] Digit { Digit } 

FloatConstant := [ - ] Digit { Digit } [ . Digit { Digit } ] 

StringConstant := " { ( CharacterLiteral | EscapedCharacter ) } " 

Digit := 0 – 9 

Alpha := A – Z | a – z 

WhiteSpace := Space | Tab | CarriageReturn | NewLine  

CharacterLiteral := Space - ! | # - [ | ] - ~ EscapedCharacter := \b | \n | \r | \t | \\ | \' | \" 

Additional Tokenizing Rules: 

•        Keywords are identifiers that are in the List provided to the Scanner.  

•        Whitespace must be skipped during the tokenizing.

•        A negative sign immediately preceding an integer or float constant must be tokenized as an operator if the previous token was a constant or identifier. For example, “A -5” must be tokenized as Identifier “A”, Operator “-”, and IntConstant “5”, not as Identifier “A”, and IntConstant “-5”.

•        If an underscore or Alpha character immediately follows a constant, the token is considered Invalid. All Alpha, Digit, and underscore characters will be part of the Invalid token.

•        If an invalid character is in a string constant, the characters are consumed until the next non-escaped " is reached or the end of stream is reached. The token type is considered Invalid.

•        Any invalid character beginning a token will be considered an Invalid token by itself. For example, “@#4” must be tokenized as Invalid “@”, Invalid “#”, and IntConstant “4”.

Implementation Requirements: 

•        You may use java.io.FileInputStream.

•        You may use java.util.Set, java.util.HashSet, java.util.Arrays and similar containers.

•        You may not use java.util.regex or similar packages.

•        You may not use java.util.StringTokenizer or similar library classes.

Your final task is to develop the CSVParser class that will rely on the PeekableCharacterStream interface. The CSVParser must have the following minimal interface.

public class CSVParser{ 

    // Constructor that takes in a stream. 

    public CSVParser(PeekableCharacterStream stream); 

  

    // Returns the next row without consuming it. If no more rows are  

    // available null is returned. 

    public Map<String,String peekNextRow(); 

 

    // Returns the next row and consumes it. If no more rows are  

    // available null is returned. 

    public Map<String,String getNextRow(); 

}