具有多个操作的Java计算器

Question

到目前为止我有以下工作正常.我确定可能有一种更简单的方法可以做到这一点,但我需要改变/改变的是Matheq的顶级方法.Math方法执行单个数学运算.

它适用于带+, - ,*和/的任何单个操作.

我的问题是解决一个更大的等式,例如10 - 10/5 + 3.然而它确实正确地解决了10/5 + 65*2.原因是每个部分,数字和操作都被拆分为字符串数组.每次操作完成后,数字和操作将替换为该等式的结果.可能看起来更令人困惑,但我想不出更好的方法.它无法解决其他方程的原因是因为我将字符串映射回字符串数组.

字符串数组示例 10-10/5 + 3 String = {10, - ,10,/,5,+,3}在操作之后先进行除法然后从左向右减去,然后加上String = {8,8,2,2,2, 5,5}

这是我的代码,有人请帮助我:

修订 改版,现在它的工作原理与上面,但仍然有一些麻烦龙方程.一个简短的例子是它解决了2*2*2*2除以5就好了但是如果改变它那么10 - 2*2*2*2除以5我得到了错误的答案.

 public class Matheq {

String fnum = null;
String lnum = null;
String total = null;

public String Matheq(String mathoperation) {

    String mathoperation= "6 * 3 - 4 * 2";

    mathoperation = mathoperation.replaceAll(",", "");
    mathoperation = mathoperation.replaceAll("plus", "+");
    mathoperation = mathoperation.replaceAll("minus", "-");
    mathoperation = mathoperation.replaceAll("times", "*");
    mathoperation = mathoperation.replaceAll("divided by", "dividedby");
    mathoperation = mathoperation.replaceAll("percent of", "percentof");
    String[] splitstr = mathoperation.split(" ");
    while(splitstr.length>1){
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("percentof") >= 0) {
        String buildit = splitstr[i-1] + " percent of " + splitstr[i+1];
        String done = math(buildit);
        System.out.println("Percentage operation: " + splitstr[i-1] + " percent of " + splitstr[i+1] + "=" + done);
        splitstr[i] = done;
        splitstr[i-1] = "";
        splitstr[i+1] = "";
        ArrayList<String> list = new ArrayList<String>();
        for(String s : splitstr){
            if(!s.equals("")){
                list.add(s);
            }
        }
        splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("dividedby") >= 0) {
            String buildit = splitstr[i-1] + " divided by " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Division operation: " + splitstr[i-1] + " divided by " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
        System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("*") >= 0) {
            String buildit = splitstr[i-1] + " * " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Multiplication operation: "+ splitstr[i-1] + " * " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
    for(int i=0; i<splitstr.length; i++) {
            System.out.println("Get value: " + splitstr[i]);
        if(splitstr[i].indexOf("+") >= 0) {
            String buildit = splitstr[i-1] + " + " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Addition operation: " + splitstr[i-1] + " + " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }
    }
        for(int i=0; i<splitstr.length; i++) {
            System.out.println("Get value: " + splitstr[i]);
            if(splitstr[i].indexOf("-") >= 0) {
            String buildit = splitstr[i-1] + " - " + splitstr[i+1];
            String done = math(buildit);
            System.out.println("Subtraction operation: " + splitstr[i-1] + " - " + splitstr[i+1] + "=" + done);
            splitstr[i] = done;
            splitstr[i-1] = "";
            splitstr[i+1] = "";
            ArrayList<String> list = new ArrayList<String>();
            for(String s : splitstr){
                if(!s.equals("")){
                    list.add(s);
                }
            }
            splitstr = list.toArray(new String[list.size()]);
        }   
    }
    for(int i=0; i<splitstr.length; i++) {  
        System.out.println("Final operation: " + total + " " + splitstr[i]);
    }
    }
    return total;

}

private String math(String mathoperation) {
    // TODO Auto-generated method stub
    if(mathoperation.contains("percent of")){
        mathoperation = mathoperation.replaceAll("percent of", "%");
        int str = mathoperation.indexOf("%");
        System.out.println(str);
        fnum = mathoperation.substring(0, str-1);
        fnum = fnum.replaceAll(" ", "");
        fnum = "." + fnum;
        System.out.println(fnum);
        double intfnum = Double.parseDouble(fnum);
        System.out.println(intfnum);
        int lastind = mathoperation.length();
        System.out.println(lastind);
        lnum = mathoperation.substring(str+1, lastind);
        lnum = lnum.replaceAll(" ", "");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intlnum * intfnum;
        System.out.println(tot);
        total = Double.toString(tot);
        if(total.length() == 3){
            total = total + "0";
        }
        if(total.length() > 5){
            total = total.substring(0, 4);
        }
        total = total.replace("0.", "");
        System.out.println("Total:" + total);
        } else 
    if(mathoperation.contains("-")){
        int str = mathoperation.indexOf("-");
        System.out.println(str);
        fnum = mathoperation.substring(0, str-1);
        fnum = fnum.replaceAll(" ", "");
        System.out.println(fnum);
        double intfnum = Double.parseDouble(fnum);
        System.out.println(intfnum);
        int lastind = mathoperation.length();
        System.out.println(lastind);
        lnum = mathoperation.substring(str+1, lastind);
        lnum = lnum.replaceAll(" ", "");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intfnum - intlnum; 
        System.out.println(tot);
        total = Double.toString(tot);
        System.out.println(total);
        } else 
    if(mathoperation.contains("+")){
        int str = mathoperation.indexOf("+");
        System.out.println(str);
        fnum = mathoperation.substring(0, str-1);
        fnum = fnum.replaceAll(" ", "");
        System.out.println(fnum);
        double intfnum = Double.parseDouble(fnum);
        System.out.println(intfnum);
        int lastind = mathoperation.length();
        System.out.println(lastind);
        lnum = mathoperation.substring(str+1, lastind);
        lnum = lnum.replaceAll(" ", "");
        System.out.println(lnum);
        double intlnum = Double.parseDouble(lnum);
        System.out.println(intlnum);
        double tot = intfnum + intlnum; 
        System.out.println(tot);
        total = Double.toString(tot);
        System.out.println(total);
        } else 
    if(mathoperation.contains("*")){
    int str = mathoperation.indexOf("*");
    System.out.println(str);
    fnum = mathoperation.substring(0, str-1);
    fnum = fnum.replaceAll(" ", "");
    System.out.println(fnum);
    double intfnum = Double.parseDouble(fnum);
    System.out.println(intfnum);
    int lastind = mathoperation.length();
    System.out.println(lastind);
    lnum = mathoperation.substring(str+1, lastind);
    lnum = lnum.replaceAll(" ", "");
    System.out.println(lnum);
    double intlnum = Double.parseDouble(lnum);
    System.out.println(intlnum);
    double tot = intfnum * intlnum; 
    System.out.println(tot);
    total = Double.toString(tot);
    System.out.println(total);
    } else
    if(mathoperation.contains("divided by")){
    mathoperation = mathoperation.replaceAll("divided by", "/");
    int str = mathoperation.indexOf("/");
    System.out.println(str);
    fnum = mathoperation.substring(0, str-1);
    fnum = fnum.replaceAll(" ", "");
    System.out.println(fnum);
    double intfnum = Double.parseDouble(fnum);
    System.out.println(intfnum);
    int lastind = mathoperation.length();
    System.out.println(lastind);
    lnum = mathoperation.substring(str+1, lastind);
    lnum = lnum.replaceAll(" ", "");
    System.out.println(lnum);
    double intlnum = Double.parseDouble(lnum);
    System.out.println(intlnum);
    double tot = intfnum / intlnum; 
    System.out.println(tot);
    total = Double.toString(tot);
    System.out.println(total);
    } else {
        total = null;
    }
    return total;
}

}

Answer 1

数组是表示解析方程的错误结构.您需要具有可以表示运算符优先级的结构.处理此类问题的典型机制是抽象语法树.对于10 - 10/5 + 3示例,您可能希望构建一个如下所示的树:

 <result>
  /   \
 '-' '+'
 / \ / \
10 '/'  3
   / \
  10  5

使用具有高优先级的操作符的这种类型的结构降低树,然后您可以执行自下而上的评估以获得正确的结果.