debug-java.rar_Debug.java_java 编译器

package calculator; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* * Created on 2004-11-30 * * TODO To change the template for this generated file go to * Window - Preferences - Java - Code Style - Code Templates */ /** * @author tom1 * * TODO To change the template for this generated type comment go to Window - * Preferences - Java - Code Style - Code Templates */ public class Calculator { private static Queue tokens = null; protected static Queue tokenize(String input) throws TokenException { Queue Q = new Queue(); //创建一个空队列 String token = new String(""); //创建一个空字符串 for (int i = 0; i < input.length(); i++) { char cc = input.charAt(i); //如果当前字符不是一个有效的操作符，就认为它是一个数的一部分 if (!TokenOperator.isValidOp(cc)) token += cc; //于是将它添加到token串的后面 else {//否则，当前存储在token中的数是一个完整的数 if (!token.trim().equals("")) //用它构造一个TokenNumeric对象，然后将它插入队列Q中 Q.enqueue(new TokenNumeric(token.trim())); //用当前字符构造一个TokenOperator，并加入到Q中 Character operator = new Character(cc); Q.enqueue(new TokenOperator(operator.toString())); token = new String(""); //令token为空，准备接收下一个数 } } if (!token.trim().equals("")) Q.enqueue(new TokenNumeric(token.trim())); return Q; } protected static Queue toPostfix(Queue infix) throws TokenException { Stack stack = new Stack(); //初始化一个空栈用于存储操作符，即为“运算符栈” Queue postfix = new Queue(); //初始化一个空的队列用于存储计算结果，即为“后缀队列” try { while (!infix.isEmpty()) { Object token = infix.dequeue(); if (token instanceof TokenNumeric) postfix.enqueue(token); //如果这个标记串是一个数，将它插入后缀队列中 else { TokenOperator op = (TokenOperator) token; if (op.isOpenParen()) stack.push(op); //如果是左括号，则压入“运算符栈” else if (op.isCloseParen()) { //如果是右括号 while (!((TokenOperator) stack.peek()).isOpenParen()) postfix.enqueue(stack.pop()); Object dummy = stack.pop(); } else if (stack.isEmpty()) stack.push(op); //如果栈空，则操作符入栈 else if (((TokenOperator) stack.peek()).order() < op .order()) //如果运算符栈的顶部的操作符的优先级小于当前标记串， stack.push(op); //则将当前标记串压入栈中 else { while ((!stack.isEmpty()) && (((TokenOperator) stack.peek()).order() >= op .order())) //将运算符栈中所有优先级大于等于当前标记串的标记串弹出栈， postfix.enqueue(stack.pop());//并将它们插入后缀队列 stack.push(op); //将当前标记串压入栈中 } } } //当表达式队列中的所有标记串都处理完后，从运算符栈中弹出剩余的标记串， //并将它们插入到后缀队列中 while (!stack.isEmpty()) { if (!((TokenOperator) stack.peek()).isOpenParen()) postfix.enqueue(stack.pop()); else throw new TokenException("unmatched bracket"); } return postfix; } catch (StackException se) { throw new TokenException("unmatched bracket or invalid input"); } catch (QueueException qe) { throw new TokenException("unknown exception"); } } protected static double evaluatePostfix(Queue postfix) throws TokenException { Stack numbers = new Stack(); try { while (!postfix.isEmpty()) { Object token = postfix.dequeue(); if (token instanceof TokenOperator) { //如果标记串是操作符 TokenNumeric n1 = (TokenNumeric) numbers.pop(); TokenNumeric n2 = (TokenNumeric) numbers.pop(); TokenOperator op = (TokenOperator) token; //根据操作符执行相应的运算，并把计算结果入栈 numbers.push(op.evaluate(n1.getNumber(), n2.getNumber())); } else numbers.push(token); //如果标记串是一个数，将它入栈 } TokenNumeric answer = (TokenNumeric) numbers.pop(); if (numbers.isEmpty()) return answer.getNumber(); else throw new TokenException("invalid expression"); } catch (StackException se) { throw new TokenException("invalid expression"); } catch (QueueException qe) { throw new TokenException("unknown error"); } } public static void main(String args[]) { String prompt = "Calc [q to quit] => "; System.out.print("Calc [q to quit] => "); BufferedReader buff = new BufferedReader(new InputStreamReader( System.in)); try { String input = buff.readLine(); while (!input.equalsIgnoreCase("q")) { if (!input.equals("")) { try { double ans = evaluatePostfix(toPostfix(tokenize(input))); System.out.println(prompt + input + " = " + ans); } catch (TokenException te) { System.err.println(te); } } System.out.print(prompt); input = buff.readLine(); } } catch (IOException ioe) { ioe.printStackTrace(); } } }