pdemo.java

解释器是用于分析简单的算术运算, 适用于初学者开发自己的智能系统.

// Demonstrate the parser

import java.io.*;

class PDemo{
  public static void main(String args[])
    throws IOException
    {
    	String expr;
    	
    	BufferedReader br = new
    	  BufferedReader(new InputStreamReader(System.in));
    	Parser p = new Parser();
    	
    	System.out.println("Enter an empty expression to stop.");
    	for(;;)
    	{
    		System.out.print("Enter expression: ");
    		expr = br.readLine();
    		if(expr.equals(""))break;
    		try
    		{
    			System.out.println("Result: " + p.evaluate(expr));
    			System.out.println();
    			
    		}catch(ParserException exc)
    		{
    			System.out.println(exc);
    		}
    		
        }
    }
}