java命令行无法识别字符串

我的代码运行得很好，但这正是折磨我的原因，我找不到答案。我无法将字符串直接从命令行参数传递到构造函数中，然后传递给构造期间调用的方法（evaluateMethod）。出于某种原因，该方法没有将其视为字符串。为什么要这样做？我让它工作的唯一方法是在我的主方法中放入if/else语句，这些语句调用构造函数并传入参数。附件是我的密码

/**
 * Program to calculate approximation, actual value, absolute error, and relative error with a definite integral
 * @author c-dub
 *
 */
public class Integrate {
    private String whichWay;
    double upper, lower, deltaX, actual, absoluteError, relativeError;  
    int rect;   

    // Constructor
    Integrate(String str, double a, double b, int n) {
        this.whichWay = str;
        this.lower = a;
        this.upper = b;
        this.rect = n;
        this.deltaX = (b - a) / rect;
        this.actual = (Math.pow(upper, 3) / 3) - (Math.pow(lower, 3) / 3);
        evaluateMethod(whichWay);
        System.out.println("Actual value: " + actual);
        System.out.println("Absolute error: " + absoluteError + ", Relative error: " + relativeError + ".");
    }    

    /**
     * Evaluates all calculations
     * @param whichWay, the string to determine left, right, trapezoid method
     */
    private void evaluateMethod(String whichWay) {
        if(whichWay == "l" || whichWay == "L") {
            System.out.println("Using left hand endpoints, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateLeft() + ".");           
        }
        else if(whichWay == "r" || whichWay == "R") {
            System.out.println("Using right hand endpoints, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateRight() + ".");          
        }
        else if(whichWay == "t" || whichWay == "T") {
            System.out.println("Using the trapezoid method, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateTrapezoid() + ".");          
        }
        else {
            throw new IllegalArgumentException("Bad string input. Please restart program");
        }
    }

    /**
     * Left hand endpoint integration
     * @return the approximate value as a double
     */
    private double integrateLeft() {        
        double sum = 0;
        // First interval to the last interval, depending on number of rectangles
        double lowerAlt = lower;
        for(int i = 0; i < rect; i++) {         
            sum += evaluate(lowerAlt);
            lowerAlt = lowerAlt + deltaX;
        }
        absoluteError = Math.abs(actual - (sum * deltaX));
        relativeError = Math.abs(absoluteError / actual);
        // Multiply entire sum by deltaX
        return Math.abs(sum * deltaX);
    }

    /**
     * Right hand endpoint integration
     * @return the approximate value as a double
     */
    private double integrateRight() {
        double sum = 0;
        // First interval to the last interval, depending on number of rectangles
        double lowerAlt = lower + deltaX;
        for(double i = 0; i < rect; i++) {
            sum += evaluate(lowerAlt);
            lowerAlt = lowerAlt + deltaX;
        }
        absoluteError = Math.abs(actual - (sum * deltaX));
        relativeError = Math.abs(absoluteError / actual);
        // Multiply entire sum by deltaX
        return Math.abs(sum * deltaX);
    }

    /**
     * Trapezoid method of integration
     * @return the approximate value as a double
     */
    private double integrateTrapezoid() {
        double sum = 0;
        // first interval after the lower bound, to the last interval before upper bound depending on # of rectangles
        double lowerAlt = lower + deltaX;
        for(int i = 1; i < rect; i++) {
            sum += evaluate(lowerAlt) * 2;
            lowerAlt = lowerAlt + deltaX;
        }
        // Now pass the lower and upper values into the function and add to total sum
        sum += evaluate(lower) + evaluate(upper);
        absoluteError = Math.abs(actual - (sum * (deltaX / 2)));
        relativeError = Math.abs(absoluteError / actual); 
        // Mulitply calculation by deltaX / 2
        return Math.abs(sum * (deltaX / 2));
    }

    /**
     * Method to define the actual function
     * @param x, function input value
     * @return the function output value f(x)
     */
    private double evaluate(double x) {
        //Please enter your desired function here:
        return Math.pow(x, 2);
    }


    /**
     * Main method
     * @param args, the command line arguments
     */
    public static void main(String[] args) {
        String str;
        double a = Double.parseDouble(args[1]);
        double b = Double.parseDouble(args[2]);
        int n = Integer.parseInt(args[3]);
        if(args[0].equals("l") || args[0].equals("L")) {
          new Integrate("l", a, b, n);
        }
        else if(args[0].equals("r") || args[0].equals("R")) {
          new Integrate("r", a, b, n);
        }
        else if(args[0].equals("t") || args[0].equals("T")) {
          new Integrate("t", a, b, n);
        }    
      }
}

/**
*用定积分计算近似值、实际值、绝对误差和相对误差的程序
*@author c-dub
*
*/
公共类集成{
私用字符串whichWay；
双上、下、deltaX、实际、绝对误差、相对误差；
int-rect；
//建造师
集成（字符串str、双a、双b、整数n）{
this.whichWay=str；
这个。下=a；
这个上=b；
this.rect=n；
this.deltaX=（b-a）/rect；
this.actual=（Math.pow（上，3）/3）-（Math.pow（下，3）/3）；
评价方法（whichWay）；
System.out.println（“实际值：+实际值”）；
System.out.println（“绝对误差：+absoluteError+”，相对误差：+relativeError+”）；
}    
/**
*评估所有计算
*@param whichWay，判断字符串左、右、梯形的方法
*/
私有void evaluateMethod（字符串whichWay）{
如果（whichWay==“l”| whichWay==“l”）{
System.out.println（“使用左手端点，在整数（“+lower+”，“+upper+”）上使用”
+矩形+“矩形…”；
System.out.println（“近似值为：“+integrateLeft（）+”）；
}
else if（whichWay==“r”| whichWay==“r”）{
System.out.println（“使用右手端点，在整数（“+lower+”，“+upper+”）上使用”
+矩形+“矩形…”；
System.out.println（“近似值为：“+integraterRight（）+”）；
}
else if（whichWay==“t”| whichWay==“t”）{
System.out.println（“使用梯形方法，在积分（“+下+”，“+上+”）上加上”
+矩形+“矩形…”；
System.out.println（“近似值为：“+integrateTrapezoid（）+”）；
}
否则{
抛出新的IllegalArgumentException（“错误的字符串输入。请重新启动程序”）；
}
}
/**
*左端点积分
*@以双精度返回近似值
*/
私有双积分函数（{
双和=0；
//第一个间隔到最后一个间隔，取决于矩形的数量
双低=低；
对于（int i=0；i

在我的evaluateMethod（）方法中，它检查字符串，即使命令args传递的是合法的字符串字母（不是字符），它也不会将其视为字符串，而是引发异常。 感谢您的评估方法（）更改whichWay==“l”与whichWay.equals（“l”）类似于main（）：

因为要比较字符串值，必须使用此函数。（见文件

private void evaluateMethod(String whichWay) {
        if(whichWay.equals("l") || whichWay.equals("L")) {
            System.out.println("Using left hand endpoints, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateLeft() + ".");           
        }
        else if(whichWay.equals("r") || whichWay.equals("R")) {
            System.out.println("Using right hand endpoints, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateRight() + ".");          
        }
        else if(whichWay.equals("t") || whichWay.equals("T")) {
            System.out.println("Using the trapezoid method, on the integral (" + lower + ", " + upper + ") with "
                                + rect + " rectangles.....");
            System.out.println("The approximate value is: " + integrateTrapezoid() + ".");          
        }
        else {
            throw new IllegalArgumentException("Bad string input. Please restart program");
        }
    }

if(whichWay == "l" || whichWay == "L")

if(whichWay.equals("l") || whichWay.equals("L")