初学java，求助。

[小一郎]

写了个简单的中缀表达式求值，一直调不过，麻烦各位大侠帮忙指正，代码如下

目标输入：（1+2）* 3 + （5/1）
目标输出： 14

package simplecomputer;

import java.util.Scanner;
import java.util.Stack;

public class Caculator
{
public String compute(String expression)
{
String exp = expression.trim();
char[] strs = exp.toCharArray();

Stack<String> operatorStack = new Stack<String>();
Stack<String> valueStack = new Stack<String>();

String topOperator = "";
String operandOne = "";
String operandTwo = "";

Double result = new Double(0.0);

for (int i = 0; i < strs.length; i++)
{
String pointer = String.valueOf(strs[i]);
Character next = new Character(pointer.charAt(0));

switch (next)
{
case '+':case '-':case '*':case '/':
if(operatorStack.isEmpty())
{
operatorStack.push(pointer);
}
else
{
topOperator = operatorStack.peek();
Character a = topOperator.charAt(0);
while (priority(next) <= priority(a))
{
topOperator = operatorStack.pop();
operandTwo = valueStack.pop();
operandOne = valueStack.pop();
Double num1 = Double.parseDouble(operandOne);
Double num2 = Double.parseDouble(operandTwo);
result = calculate(topOperator,num1, num2);
valueStack.push(result.toString());
}
operatorStack.push(pointer);
}
break;

case '(':
operatorStack.push(pointer);
break;

case ')':
topOperator = operatorStack.pop();
while(topOperator != "(")
{
operandTwo = valueStack.pop();
operandOne = valueStack.pop();
Double num1 = Double.parseDouble(operandOne);
Double num2 = Double.parseDouble(operandTwo);
result = calculate(topOperator,num1, num2);
valueStack.push(result.toString());

topOperator = operatorStack.pop();
}
break;
default:
if (Character.isDigit(next))
{
valueStack.push(pointer);
}
else
{
System.out.println("表达式输入错误");
}
break;
}
}

while (!operatorStack.isEmpty())
{
System.out.println(valueStack);
System.out.println(operatorStack);

topOperator = operatorStack.pop();
operandTwo = valueStack.pop();
operandOne = valueStack.pop();
Double num1 = Double.parseDouble(operandOne);
Double num2 = Double.parseDouble(operandTwo);
result = calculate(topOperator,num1, num2);
valueStack.push(result.toString());
}


return valueStack.peek();
}

private int priority(Character op) //计算运算符优先级
{
Character add = new Character('+');
Character reduce = new Character('-');
Character minus = new Character('*');
Character dive = new Character('/');

if( (op.equals(add))||(op.equals(reduce)) )
{
return 1;
}
else if ( (op.equals(minus))||(op.equals(dive)) )
{
return 2;
}
else
{
return 0;
}
}

public Double calculate(String op, Double num1, Double num2)
{
if ("+".equals(op))
{
return num1 + num2;
}
if ("-".equals(op))
{
return num1 - num2;
}
if ("*".equals(op))
{
return num1 * num2;
}
if ("/".equals(op))
{
if (num2.equals(0.0))
{
System.out.println("Error");
}
else
{
return num1 / num2;
}
}
return null;
}

public static void main(String arg[])
{
String expression = "";
System.out.println("输入计算表达式：");
Scanner temp = new Scanner(System.in);
expression = temp.next();
System.out.println(expression);

Caculator b = new Caculator();
String res = b.compute(expression);
System.out.println("计算结果是：" + res);
}
}

[q345911220]

+_+有点复杂。。。

[vsking]

Java虽然可以java虽然可以在不同手机上运行，但是效率很低,还不如不同平台针对性开发
java虽然可以跨平台,一般都是一次编译，到处异常，不断调试
java jdk升级太慢，不能提供给开发人员高效开发支撑,String.isNullOrEmpty;String.isNullOrWhiteSpace有么
java ide(myeclipse,netbean)提供的智能提示，调试等功能也不足以提供给开发人员高效开发和调试
java jdk代码运行效率完全不能和.net相提并论,比如泛型，键值对搜索。。。。。。

[buzaibeishang4617016]

哦，没调试出来，期待大虾解决

[signinchina]

用myeclipse调一下就可以了

[lodachi]

[Quote=引用 3 楼 vsking 的回复:]

Java虽然可以java虽然可以在不同手机上运行，但是效率很低,还不如不同平台针对性开发
java虽然可以跨平台,一般都是一次编译，到处异常，不断调试
java jdk升级太慢，不能提供给开发人员高效开发支撑,String.isNullOrEmpty;String.isNullOrWhiteSpace有么
java ide(myeclipse,netbean)提供的智能提示，调试等功能也不……
[/Quote]死一边去

[lodachi]

jdk1.4环境下调通过 请问楼主哪调不过 报什么错 描述清楚好不 浪费大家时间 请原谅我说话就这么直

import java.util.Scanner;
import java.util.Stack;

public class Caculator {
	public String compute(String expression) {
		String exp = expression.trim();
		char[] strs = exp.toCharArray();

		Stack operatorStack = new Stack();
		Stack valueStack = new Stack();

		String topOperator = "";
		String operandOne = "";
		String operandTwo = "";

		double result = 0.0;

		for (int i = 0; i < strs.length; i++) {
			String pointer = String.valueOf(strs[i]);
			Character next = new Character(pointer.charAt(0));

			switch (next.charValue()) {
			case '+':
			case '-':
			case '*':
			case '/':
				if (operatorStack.isEmpty()) {
					operatorStack.push(pointer);
				} else {
					topOperator = operatorStack.peek().toString();
					Character a = new Character(topOperator.charAt(0));
					while (priority(next) <= priority(a)) {
						topOperator = operatorStack.pop().toString();
						operandTwo = valueStack.pop().toString();
						operandOne = valueStack.pop().toString();
						Double num1 = Double.valueOf(operandOne);
						Double num2 = Double.valueOf(operandTwo);
						result = calculate(topOperator, num1, num2);
						valueStack.push(String.valueOf(result));
					}
					operatorStack.push(pointer);
				}
				break;

			case '(':
				operatorStack.push(pointer);
				break;

			case ')':
				topOperator = operatorStack.pop().toString();
				while (topOperator != "(") {
					operandTwo = valueStack.pop().toString();
					operandOne = valueStack.pop().toString();
					Double num1 = Double.valueOf(operandOne);
					Double num2 = Double.valueOf(operandTwo);
					result = calculate(topOperator, num1, num2);
					valueStack.push(String.valueOf(result));

					topOperator = operatorStack.pop().toString();
				}
				break;
			default:
				if (Character.isDigit(next.charValue())) {
					valueStack.push(pointer);
				} else {
					System.out.println("表达式输入错误");
				}
				break;
			}
		}

		while (!operatorStack.isEmpty()) {
			System.out.println(valueStack);
			System.out.println(operatorStack);

			topOperator = operatorStack.pop().toString();
			operandTwo = valueStack.pop().toString();
			operandOne = valueStack.pop().toString();
			Double num1 = Double.valueOf(operandOne);
			Double num2 = Double.valueOf(operandTwo);
			result = calculate(topOperator, num1, num2);
			valueStack.push(String.valueOf(result));
		}

		return valueStack.peek().toString();
	}

	private int priority(Character op) // 计算运算符优先级
	{
		Character add = new Character('+');
		Character reduce = new Character('-');
		Character minus = new Character('*');
		Character dive = new Character('/');

		if ((op.equals(add)) || (op.equals(reduce))) {
			return 1;
		} else if ((op.equals(minus)) || (op.equals(dive))) {
			return 2;
		} else {
			return 0;
		}
	}

	public double calculate(String op, Double num1, Double num2) {
		if ("+".equals(op)) {
			return num1 .doubleValue()+ num2.doubleValue();
		}
		if ("-".equals(op)) {
			return num1.doubleValue() - num2.doubleValue();
		}
		if ("*".equals(op)) {
			return num1.doubleValue() * num2.doubleValue();
		}
		if ("/".equals(op)) {
			if (num2.equals(new Double(0.0))) {
				System.out.println("Error");
			} else {
				return num1.doubleValue() / num2.doubleValue();
			}
		}
		return 0;
	}

	public static void main(String arg[]) {
		String expression = "";
		System.out.println("输入计算表达式：");
		Scanner temp = new Scanner(System.in);
		expression = temp.next();
		System.out.println(expression);

		Caculator b = new Caculator();
		String res = b.compute(expression);
		System.out.println("计算结果是：" + res);
	}
}

[小一郎]

我用的jdk1.5

输入计算表达式：
（1+2）* 3 + （5/1）
（1+2）*
Exception in thread "main" java.util.EmptyStackException
at java.util.Stack.peek(Stack.java:79)
at java.util.Stack.pop(Stack.java:61)
at simplecomputer.Caculator.compute(Caculator.java:91)
at simplecomputer.Caculator.main(Caculator.java:161)
表达式输入错误
表达式输入错误
[1, 2]
[+, *]
[2.0]
[+]


[Quote=引用 7 楼 lodachi 的回复:]
jdk1.4环境下调通过 请问楼主哪调不过 报什么错 描述清楚好不 浪费大家时间 请原谅我说话就这么直

Java code


import java.util.Scanner;
import java.util.Stack;

public class Caculator {
public String compute(String expression) {
……
[/Quote]

[bobo364]

貌似没啥问题，但我有个问题，借你的贴，问一下，计算器如何记忆上次的结果和后面的东西运算啊？我想搞个计算器，一次没问题，多次就碰到麻烦了

[dsfsdfsdfdfsdfdsfdsf]

额 ...