我得到的错误：无法找到符号 构造方法Token。但是我愿意 在Token类中有一个构造函数
无法找到符号变量 令牌代码。我明显地用它了 我认为我正确地初始化它 那怎么了？
无法找到符号变量scantest。 我有相同的文件夹所有 课程是为什么不读它？
import java.io.BufferedReader; import java.io.FileReader; import java.io。*;
public class scanner implements CompilerConstants {
private char c;
private BufferedReader source;
public int token;
private String attr = "";
//private int val = '0';
private
public scanner(BufferedReader buffer) {
source = buffer;
getChar();
} //constructor of scanner
public void getChar()
{
c = (char)(source.read());
//do a read in
}
//lookup for finding identifiers
public boolean lookup(String word)
{
boolean check = false;
for(int i=0; i < RESERVEDWORD.length;i++)
if(word==(RESERVEDWORD[i]))
{
check = true;
}
return check;
}
//public boolean T(int tcc, String attt) //to return token
//{
// tokenCode = tcc;
// attribute = attt;
// return T;
// }
public Token nextToken() throws IOException
{
attr = "";
//need to save to do lookup see if its identifier or not
while(c!=EOFCHAR); //if not end of file then do
{
while (Character.isWhitespace(c))//remove white space, check whether is letter or digit
{
getChar();
}
if (Character.isLetter(c))
{
while(Character.isLetterOrDigit(c))
{
attr = attr + c;
getChar();
}
return new Token(lookup(attr), attr); //
}
else if (Character.isDigit(c)) {
while(Character.isDigit(c))
{
attr = attr + c;
getChar();
}
return new Token(NUMBER, attr);
}
else {
switch (c) {
case '<' : getChar();
if(c=='>')
{
getChar();
return new Token(NE, null);
}
else if (c=='=')
{
getChar();
return new Token(LE, null);
}
return new Token(LT, null);
case '>' : getChar();
if(c=='<')
{
getChar();
return new Token(NE, null);
}
else if (c=='=')
{
getChar();
return new Token(GE, null);
}
return new Token(GT, null);
case '=' : getChar();
return new Token(EQ, null);
case '|' : getChar();
return new Token(OR, null);
case '+' : getChar();
return new Token(PLUS, null);
case '-' : getChar();
return new Token(MINUS, null);
case '*' : getChar();
return new Token(TIMES, null);
case '/' : getChar();
return new Token(DIVIDE, null);
case '[' : getChar();
return new Token(LEFTSQ, null);
case ']' : getChar();
return new Token(RIGHTSQ, null);
case '(' : getChar();
return new Token(LEFTPAREN, null);
case ')' : getChar();
return new Token(RIGHTPAREN, null);
case ',' : getChar();
return new Token(COMMA, null);
case EOFCHAR : getChar();
return new Token(EOF, null);
}
} // switch
//return EOF.Token;
return Token(tokenCode, attr); //tokenAttribute
} // if
// return Token;
} // getToken
public static void main(String[] args)
{
BufferedReader source = new BufferedReader(new FileReader(scantest.echo));
}
}
Token class
public class Token implements CompilerConstants {
private int tokenCode;
private String attribute;
public Token(int tc, String att) //constructor
{
tokenCode = tc;
attribute = att;
}
public int getToken()//return tokencode
{
return tokenCode;
}
//return token attribute
public String tokenAttribute()
{
return attribute;
}
public String toString(){
String tokenString = tokenCode + " ";
switch (tokenCode) { //// relational expressions for metasymbols
case AND: return (tokenString + "/n AND");
case IDENTIFIER: return (tokenString + "/n IDENTIFIER" + attribute);
case OR: return (tokenString + "/n OR");
case NOT: return (tokenString + "/n NOT");
case ARRAY: return (tokenString + "/n ARRAY");
case BEGIN: return (tokenString + "/n BEGIN ");
case BOOLEAN: return (tokenString + "/n BOOLEAN ");
case DO: return (tokenString + "/n DO ");
case ELSE: return (tokenString + "/n ELSE");
case END: return (tokenString + "/n END");
case FOR: return (tokenString + "/n FOR");
case FROM: return (tokenString + "/n FROM");
case IF: return (tokenString + "/n IF");
case INTEGER: return (tokenString + "/n INTEGER");
case PROCEDURE: return (tokenString + "/n PROCEDURE");
case PROGRAM: return (tokenString + "/n PROGAM");
case READ: return (tokenString + "/n READ");
case START: return (tokenString + "/n START");
case THEN: return (tokenString + "/n THEN");
case TO: return (tokenString + "/n TO");
case TRUE: return (tokenString + "/n TRUE");
case WHILE: return (tokenString + "/n WHILE");
case WRITE: return (tokenString + "/n WRITE");
case WRITELN: return (tokenString + "/n WRITELN");
case NUMBER: return (tokenString + "/n NUMBER" + attribute);
case STRING: return (tokenString + "/n STRING" + attribute);
case LT: return (tokenString + "/n LT");
case LE: return (tokenString + "/n LE");
case GT: return (tokenString + "/n GT");
case GE: return (tokenString + "/n GE");
case EQ: return (tokenString + "/n EQ");
case NE: return (tokenString + "/n NE");
case PLUS: return (tokenString + "/n PLUS");
case MINUS: return (tokenString + "/n MINUS");
case TIMES: return (tokenString + "/n TIMES");
case DIVIDE: return (tokenString + "/n DIVIDE");
case LEFTSQ: return (tokenString + "/n LEFTSQ");
case RIGHTSQ: return (tokenString + "/n RIGHTSQ");
case LEFTPAREN: return (tokenString + "/n LEFTPAREN");
case COLONEQUAL: return (tokenString + "/n COLONEQUAL");
case COMMA: return (tokenString + "/n COMMA");
case EOF: return (tokenString + "/n EOF");
}
return tokenString;
}
}
CompilerConstants
public interface CompilerConstants {
public static final int AND = 1;
public static final int ARRAY = 2;
public static final int BEGIN = 3;
public static final int BOOLEAN = 4;
public static final int DO = 5;
public static final int ELSE = 6;
public static final int END = 7;
public static final int FALSE = 8;
public static final int FOR = 9;
public static final int FROM = 10;
public static final int IF = 11;
public static final int INTEGER = 12;
public static final int NOT = 13;
public static final int OR = 14;
public static final int PROCEDURE = 15;
public static final int PROGRAM = 16;
public static final int READ = 17;
public static final int START = 18;
public static final int THEN = 19;
public static final int TO = 20;
public static final int TRUE = 21;
public static final int WHILE = 22;
public static final int WRITE = 23;
public static final int WRITELN = 24;
public static final int IDENTIFIER = 30;
public static final int NUMBER = 31;
public static final int STRING = 32;
public static final int LT = 33;
public static final int LE = 34;
public static final int GT = 35;
public static final int GE = 36;
public static final int EQ = 37;
public static final int NE = 38;
public static final int PLUS = 39;
public static final int MINUS = 40;
public static final int TIMES = 41;
public static final int DIVIDE = 42;
public static final int LEFTSQ = 43;
public static final int RIGHTSQ = 44;
public static final int LEFTPAREN = 45;
public static final int RIGHTPAREN = 46;
public static final int COLONEQUAL = 47;
public static final int COMMA = 48;
public static final int EOF = 99;
public static final char EOFCHAR = (char)(-1);
public static final String[] RESERVEDWORD = {"","and","array","begin","boolean",
"do","else","end","false","for","from","if","integer","not","or",
"procedure","program","read","start","then","to","true","while",
"write","writeln"};
public static final boolean DEBUG = true;
} // interface CompilerConstants
答案 0 :(得分：2)
这一行存在问题：
return new Token(lookup(attr), attr);
方法lookup(attr)返回一个布尔值，但Token构造函数期望int作为第一个参数。我可以看到：
public Token(int, String)
但不是：
public Token(boolean, String)
也许您将错误的参数传递给现有的Token构造函数。
现在，关于这一行：
return Token(tokenCode, attr); //tokenAttribute
tokenCode确实没有定义。你在哪里初始化它？你在哪里用它？
最后，关于：
new FileReader(scantest.echo));
由于您没有提供课程来源，因此很难回答。什么是回声？一个静态属性？
PS：您的课程应以大写字母开头和/或使用Scanner或ScanTest而不是scanner和scantest等骆驼案例表示法。这是推荐的惯例。