java - j2me : Works only for single digit operands 中的算术表达式求值

Question

我已经实现了我在 this link 上找到的算法来评估 j2me 的算术表达式。但只有当我有一位数操作数时它才能正常工作，即 2、5、7、3 但不是 456、56、34.45 等。我做了一些更改，因为我知道我必须添加不是一个一个地找到的数字，但直到我们以数字结尾。然后我也找到了 this link，但事情仍然没有像预期的那样顺利。首先，我尝试了 exp4j 库，但我猜它在 j2me 上不起作用。代码现在变得非常困惑。我可以就如何解决这个问题发表任何意见吗？如有任何帮助，我们将不胜感激。

最初仅适用于个位数操作数的代码:

import java.util.Stack;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;

public class SampleInfixToPostfixToResult {

static Stack stack=new Stack();
static StringBuffer p=new StringBuffer();
static Vector v=new Vector();

public static StringBuffer toPostfix(String q)
{
for(int i=0;i<q.length();i++)
{
    if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
    {
        p.append(q.charAt(i));
    }
    else if(q.charAt(i)=='(')
    {
         stack.push(q.charAt(i));
    }
    else if(q.charAt(i)==')')
    {
        for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
        {
            p.append(stack.pop());
        }
        stack.pop();
    }
    else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
    {
        if(stack.empty()||stack.peek().equals('('))
            stack.push(q.charAt(i));
        else
        {
            while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
            {
                p.append(stack.pop());
            }
            stack.push(q.charAt(i));
        }
    }
}
while(!stack.empty())
{
    p.append(stack.pop());
}
System.out.println(p);
return p;
}


public static boolean isHigh(char op, Object AtStack)
{
char opAtStack=AtStack.toString().charAt(0);
boolean isHigh=false;
if((op==opAtStack))
    isHigh=true;
if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
{
    isHigh=true;
}
if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
{
    isHigh=true;
}
    return isHigh;
}

public static double result(StringBuffer p)
{

for(int i=0;i<p.length();i++)
{
    System.out.println(p.charAt(i));
    if(p.charAt(i)=='0'||p.charAt(i)=='1'||p.charAt(i)=='2'||p.charAt(i)=='3'||p.charAt(i)=='4'||p.charAt(i)=='5'||p.charAt(i)=='6'||p.charAt(i)=='7'||p.charAt(i)=='8'||p.charAt(i)=='9')
    {
        stack.push(p.charAt(i));
    }
    if(p.charAt(i)=='+'||p.charAt(i)=='-'||p.charAt(i)=='/'||p.charAt(i)=='*')
    {
        double a=Double.parseDouble(stack.pop().toString());
        double b=Double.parseDouble(stack.pop().toString());
        if(p.charAt(i)=='+')
        {
            stack.push(b+a);
        }
        else if(p.charAt(i)=='-')
        {
            stack.push(b-a);
        }
        else if(p.charAt(i)=='/')
        {
            stack.push(b/a);
        }
        else if(p.charAt(i)=='*')
        {
            stack.push(b*a);
        }
    }
}
System.out.println(stack);
return 0;
}

public static void main(String[] args) {
    // TODO code application logic here
    String s=new String("65*(76+2)-0/4+(2*5-6*(2*5))");


    SampleInfixToPostfixToResult.result(SampleInfixToPostfixToResult.toPostfix(s));
    System.out.println(66*(76+2)-0/4+(2*5-6*(2*5)));
}
}

我为评估多位操作数而工作的更新代码(真的搞砸了)

import java.util.Stack;
import java.util.Vector;
import java.util.logging.Level;
import java.util.logging.Logger;

public class SampleInfixToPostfixToResult {

static Stack stack=new Stack();
static StringBuffer p=new StringBuffer();
static Vector v=new Vector();

public static Vector toPostfix(String q) 
{
for(int i=0;i<q.length();i++)
{
    if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
    {
        StringBuffer tn=new StringBuffer();
        while(i<q.length()&&(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9'))
        {
             tn.append(q.charAt(i++));
        }

        v.add(tn);

    }
    else if(q.charAt(i)=='(')
    {
         stack.push(q.charAt(i));
    }
    else if(q.charAt(i)==')')
    {
        for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
        {
            v.add(stack.pop());
        }
        stack.pop();
    }
    else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
    {
        if(stack.empty()||stack.peek().equals('('))
            stack.push(q.charAt(i));
        else
        {
            while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
            {
                v.add(stack.pop());
            }
            stack.push(q.charAt(i));
        }
    }
}
while(!stack.empty())
{
    v.add(stack.pop());
}

return v;
}

public static boolean isHigh(char op, Object AtStack)
{
char opAtStack=AtStack.toString().charAt(0);
boolean isHigh=false;
if((op==opAtStack))
    isHigh=true;
if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
{
    isHigh=true;
}
if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
{
    isHigh=true;
}
    return isHigh;
}

public static double result(Vector p)
{

for(int i=0;i<p.size();i++)
{
    System.out.println(p.get(i));
    if(p.get(i)=="0"||p.get(i)=="1"||p.get(i)=="2"||p.get(i)=="3"||p.get(i)=="4"||p.get(i)=="5"||p.get(i)=="6"||p.get(i)=="7"||p.get(i)=="8"||p.get(i)=="9")
    {
         StringBuffer tn=new StringBuffer();
        while(i<p.size()&&(p.get(i)=="0"||p.get(i)=="1"||p.get(i)=="2"||p.get(i)=="3"||p.get(i)=="4"||p.get(i)=="5"||p.get(i)=="6"||p.get(i)=="7"||p.get(i)=="8"||p.get(i)=="9"))
        {
             tn.append(p.get(i++));
        }
        System.out.println("This is the full number :"+tn);
        stack.push(tn);
    }
    if(p.get(i)=="+"||p.get(i)=="-"||p.get(i)=="/"||p.get(i)=="*")
    {
        double a=Double.parseDouble(stack.pop().toString());
        double b=Double.parseDouble(stack.pop().toString());
        if(p.get(i)=="+")
        {
            stack.push(b+a);
        }
        else if(p.get(i)=="-")
        {
            stack.push(b-a);
        }
        else if(p.get(i)=="/")
        {
            stack.push(b/a);
        }
        else if(p.get(i)=="*")
        {
            stack.push(b*a);
        }
    }
}
System.out.println("Final value: "+stack);
return 0;
}

public static void main(String[] args) {
    // TODO code application logic here
    String s=new String("65*(79+22)-0/4+(29*5-6*(2*5))");

    SampleInfixToPostfixToResult.result(SampleInfixToPostfixToResult.toPostfix(s));
    //System.out.println(65*(79+22)-0/4+(29*5-6*(2*5)));
}
}

Answer 1

解决方法:

1.Function toPostfix() 现在返回栈而不是 vector ，因为现在后缀表达式被添加到栈中，例如 [34,57.+] 等。

2.通过遍历字符串直到我们有一个数字来编辑将所有数字存储到堆栈的代码。(请参见第 29 行之前的代码)

import java.util.Stack;
import java.util.Vector;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author Sandeep
 */
public class Main {
    static Stack stack=new Stack();
    static Stack stackT=new Stack();
    //static Vector v=new Vector();
    //static StringBuffer p=new StringBuffer();

    public static Stack toPostfix(String q)
{

    for(int i=0;i<q.length();i++)
    {   
        if(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
        {
            StringBuffer p=new StringBuffer();
            while(q.charAt(i)=='0'||q.charAt(i)=='1'||q.charAt(i)=='2'||q.charAt(i)=='3'||q.charAt(i)=='4'||q.charAt(i)=='5'||q.charAt(i)=='6'||q.charAt(i)=='7'||q.charAt(i)=='8'||q.charAt(i)=='9')
                    p.append(q.charAt(i++));
            stackT.push(p);
            i--;
        }
        else if(q.charAt(i)=='(')
        {
             stack.push(q.charAt(i));
        }
        else if(q.charAt(i)==')')
        {
            for(int j=0;!stack.empty()&&!stack.peek().equals('(');j++)
            {
                stackT.push(stack.pop().toString());
            }
            stack.pop();
        }
        else if(q.charAt(i)=='+'||q.charAt(i)=='-'||q.charAt(i)=='/'||q.charAt(i)=='*')
        {
            if(stack.empty()||stack.peek().equals('('))
                stack.push(q.charAt(i));
            else
            {
                while(!stack.empty()&&!stack.peek().equals('(')&&isHigh(q.charAt(i), stack.peek()))
                {
                    stackT.push(stack.pop().toString());
                }
                stack.push(q.charAt(i));
            }
        }
    }
   while(!stack.empty())
    {
        stackT.push(stack.pop().toString());
    }

       System.out.println(stackT);
    return stackT;
}

//problem lies here
public static boolean isHigh(char op, Object AtStack)
{
    char opAtStack=AtStack.toString().charAt(0);
    boolean isHigh=false;
    if((op==opAtStack))
        isHigh=true;
    if((op=='+'||op=='-')&&(opAtStack=='/'||opAtStack=='*'))
    {
        isHigh=true;
    }
    if((op=='+'&&opAtStack=='-')||(op=='-'&&opAtStack=='+')||(op=='/'&&opAtStack=='*')||(op=='*'&&opAtStack=='/'))
    {
        isHigh=true;
    }
        return isHigh;
}

public static double result(Stack p)
{

    for(int i=0;i<p.size();i++)
    {   
        if(p.get(i).toString().startsWith("0")||p.get(i).toString().startsWith("1")||p.get(i).toString().startsWith("2")||p.get(i).toString().startsWith("3")||p.get(i).toString().startsWith("4")||p.get(i).toString().startsWith("5")||p.get(i).toString().startsWith("6")||p.get(i).toString().startsWith("7")||p.get(i).toString().startsWith("8")||p.get(i).toString().startsWith("9"))
        {
            stack.push(p.get(i));
        }
        if(p.get(i).toString().equals("+")||p.get(i).toString().equals("-")||p.get(i).toString().equals("/")||p.get(i).toString().equals("*"))
        {
            double a=Double.parseDouble(stack.pop().toString());
            double b=Double.parseDouble(stack.pop().toString());
            if(p.get(i).equals("+"))
            {
                stack.push(b+a);
            }
            else if(p.get(i).equals("-"))
            {
                stack.push(b-a);
            }
            else if(p.get(i).equals("/"))
            {
                stack.push(b/a);
            }
            else if(p.get(i).equals("*"))
            {
                stack.push(b*a);
            }
        }
    }
    System.out.println(stack);
    return 0;
}

public static void main(String[] args) {
        // TODO code application logic here
        String s=new String("159*(79+23)-10/4+(22*54-67*(25*58))");
        Main.result(Main.toPostfix(s));
        System.out.println(159*(79+23)-10/4+(22*54-67*(25*58)));
    }
}