Question

当我尝试运行此代码时，我一直收到此错误＆＃34;线程＆＃39;主要＆＃39;中的例外情况java.lang.NoClassDefFoundError：main＆＃34;。谁能帮我吗？这是我的代码。此外，我必须使用缓冲读取器来读取输入，但我无法弄清楚如何实现我已经拥有的。任何帮助都会很棒！

import java.util.Arrays;

    public class StatPackage {

    private int i, numScores, place;
    private double sum, mean, median, sumOfSquares, variance, stdDev;
    private double [] inputs;
    private double [] reducedArray;
    private int [] histogramArray;
    private final int MAX = 500;


    //constructor
    public StatPackage(){
        inputs = new double[MAX]; //creates array
        numScores = 0; // count is 0
        histogramArray = new int[MAX];

    }


    public void Histogram(){
        //histogramArray = Arrays.copyOf(inputs, MAX);

        for (i = 0; i < numScores; i++){ 

            //place = (int)(inputs[i]/10);

            if (inputs[i] > 0 && inputs[i] <= 10){ histogramArray[0]+=1;}
            if (inputs[i] > 10 && inputs[i] <= 20){ histogramArray[1]+=1;}
            if (inputs[i] > 20 && inputs[i] <= 30){ histogramArray[2]+=1;}
            if (inputs[i] > 30 && inputs[i] <= 40){ histogramArray[3]+=1;}
            if (inputs[i] > 40 && inputs[i] <= 50){ histogramArray[4]+=1;}
            if (inputs[i] > 50 && inputs[i] <= 60){ histogramArray[5]+=1;}
            if (inputs[i] > 60 && inputs[i] <= 70){ histogramArray[6]+=1;}
            if (inputs[i] > 70 && inputs[i] <= 80){ histogramArray[7]+=1;}
            if (inputs[i] > 80 && inputs[i] <= 90){ histogramArray[8]+=1;}
            if (inputs[i] > 90 && inputs[i] <= 100){ histogramArray[9]+=1;}

        }
        System.out.print(" 1 - 10  | ");
        for (i = 0; i < (histogramArray[0]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("11 - 20  | ");
        for (i = 0; i < (histogramArray[1]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("21 - 30  | ");
        for (i = 0; i < (histogramArray[2]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("31 - 40  | ");
        for (i = 0; i < (histogramArray[3]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("41 - 50  | ");
        for (i = 0; i < (histogramArray[4]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("51 - 60  | ");
        for (i = 0; i < (histogramArray[5]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("61 - 70  | ");
        for (i = 0; i < (histogramArray[6]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("71 - 80  | ");
        for (i = 0; i < (histogramArray[7]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("81 - 90  | ");
        for (i = 0; i < (histogramArray[8]/5); i++){
        System.out.print("*");
        }
        System.out.println();
        System.out.print("91 - 100 | ");
        for (i = 0; i < ((histogramArray[9]/5) + (histogramArray[10]/5)); i++){
        System.out.print("*");
        }
        System.out.println();
    }   
    //go through each value of reducedArray, find out what numbers it is between, and increment array value by 1. 
// so if the test score is 35, increment reducedArray[3] by 1. then, divide each array index by 5, print that number of stars. 



    //insert scores into inputs array
    public void insert (double val){
        if (numScores < MAX){
            inputs[numScores] = val;
            numScores++;
            reducedArray = Arrays.copyOf(inputs, numScores);
        }
    }

     double Mean() {
        for (i = 0; i < numScores; i++){
            sum += reducedArray[i];
        }   
        mean = (sum/numScores);
        return mean;            
    }

     double Median(){
        Arrays.sort(reducedArray);
        double num1 = reducedArray[(numScores/2)];
        double num2 = reducedArray[((numScores/2)-1)];

        if (numScores % 2 == 0){
            median = ((num1 + num2)/2);
        }
        if (numScores % 2 != 0){
            median = reducedArray[(numScores/2)];       
        }
        return median;
    }

     double Variance(){

        sum = 0;
        for (i = 0; i < MAX; i++){
            sumOfSquares += (inputs[i]*inputs[i]);
        }
        for (i = 0; i < MAX; i++){
            sum = sum + inputs[i];
        }
        variance = ((sumOfSquares/numScores) - (sum * sum)/(numScores * numScores));
        return variance;
    }

     double StdDev (double varianceinput){
        stdDev = Math.sqrt(varianceinput);
        return stdDev;
    }
    }

Answer 1

你的班级没有主要方法。作为第一步，尝试添加以下内容：

  public static void main(String[] args) {
    final StatPackage statPackage = new StatPackage();
    statPackage.Histogram();
  }

主要方法是Java的切入点。每个可执行的Java程序都需要一个。

Answer 2

线程“main”中的异常java.lang.NoClassDefFoundError： 首先检查你的班级名称和保存的文件名是否相同？不等于这两个名字你可以得到上面的错误。记住这些名称区分大小写。例如： - 保存文件名 - t est.java 类名： T \ test.java（在textpad中）那么你可以得到以上错误。

＆＃34;线程＆＃39;主要＆＃39;中的例外情况java.lang.NoClassDefFoundError：main＆＃34;。

2 个答案: