symbol.java

java编的PL/0词法编译器

//关键字及运算符,界符表
package compiler;

import java.util.*;
/**
 * <p>Title: </p>
 * <p>Description: </p>
 * <p>Copyright: Copyright (c) 2005</p>
 * <p>Company: </p>
 * @author not attributable
 * @version 1.0
 */

public final class Symbol {
  private Symbol() {
  }

  //不要改变以下常量声明的顺序
  public static final int CONST=0;//const
  public static final int VAR=1;//var
  public static final int PROCEDURE=2;//procedure
  public static final int BEGIN=3;//begin
  public static final int END=4;//end
  public static final int IF=5;//if
  public static final int THEN=6;//then
  public static final int WHILE=7;//while
  public static final int DO=8;//do
  public static final int CALL=9;//call
  public static final int READ=10;//read
  public static final int WRITE=11;//write
  public static final int LEFT_BRACKET=12;// (
  public static final int RIGHT_BRACKET=13;// )
  public static final int SEMOCOLON=14;// ;
  public static final int EQUAL=15;// =
  public static final int EVALUATE=16;// :=
  public static final int PLUS=17;// +
  public static final int SUB=18;// -
  public static final int MUL=19;// *
  public static final int DIV=20;// /
  public static final int UNEQUAL=21;// #
  public static final int GREATER=22;// >
  public static final int GE=23;// >=
  public static final int LESS=24;// <
  public static final int LE=25;// <=
  public static final int COMMA=26;// ,

  private static int[] symbolTable={CONST,VAR,PROCEDURE,BEGIN,END,IF,THEN,
  WHILE,DO,CALL,READ,WRITE,LEFT_BRACKET,RIGHT_BRACKET,SEMOCOLON,EQUAL,EVALUATE,
  PLUS,SUB,MUL,DIV,UNEQUAL,GREATER,GE,LESS,LE,COMMA};//关键字标识数组

  private static String[] strKeyword={"const","var","procedure","begin","end","if",
      "then","while","do","call","read","write"};//关键字数组
  private static String[] strOperator={"(",")",";","=",":=","+","-","*","/","#",">",
      ">=","<","<=",","};//运算符及界符数组

  public static final HashMap hKeyword=new HashMap();//关键字散列表
  public static final HashMap hOperator=new HashMap();//运算符及界符散列表

  //对hKeyword和hOperator的每一个元素进行初始化
  static{
    for(int i=0;i<strKeyword.length;i++){
      hKeyword.put(strKeyword[i],(""+symbolTable[i]));
    }
    for(int i=0;i<strOperator.length;i++){
      hOperator.put(strOperator[i],(""+symbolTable[i+strKeyword.length]));
    }
  }
}