Java - 2D 数组 - 主类和可实例化类 - 循环错误

Question

我获得了有关 App 类和循环的帮助。

我遇到的错误是:

线程“main”中出现异常 java.lang.ArrayIndexOutOfBoundsException: 0在降雨量.Rainfall.compute引用:

   sum[i] = rain[i][j] + sum[i];

在rainfall.RainfallApp.main 引用:

    r.compute();)

C:\Users\~\run.xml:53: Java 返回: 1构建失败(总时间:5 秒)

可实例化类:

    import java.util.Arrays;
    import javax.swing.JOptionPane;

    public class Rainfall {
private int i;
private int j;
private int[][] rain = new int[4][7];
private int[] average = new int[4]; 
private int[] sum = new int[4];

public Rainfall(){
    i = 0;
    j = 0;
    rain = new int[][]{};
    average = new int[]{};
    sum = new int[]{};
}

public Rainfall(int i, int j) {
    this.i = i;
    this.j = j;
}

public int getJ() {
    return j;
}

public void setJ(int j) {
    this.j = j;
}

public int getI() {
    return i;
}

public void setI(int i) {
    this.i = i;
}

public int[][] getRain() {
    return rain;
}

public void setRain(int[][] rain) {
    this.rain = rain;
}

public int[] getAverage() {
    return average;
}

public void setAverage(int[] average) {
    this.average = average;
}

public int[] getSum() {
    return sum;
}

public void setSum(int[] sum) {
    this.sum = sum;
}

public void compute(){

    for (i = 0; i < rain.length; i++) {

        for (j = 0; j < rain[0].length; j++) {
            rain[i][j] = Integer.parseInt(JOptionPane.showInputDialog(null, "Enter value"));

            sum[i] = rain[i][j] + sum[i];
        }

        average[i] = sum[i] / rain[i].length;

    }
}

public String returnAvg(){
    return Arrays.toString(average);
}
}

APP文件:

    import javax.swing.JOptionPane;
    import java.util.Arrays;

    public class RainfallApp {

    public static void main(String[] args) {

    int[][] rain = new int[4][7];
    int[] average = new int[4];



    Rainfall r = new Rainfall();

    r.setRain(rain);
    r.compute();
    average = r.getAverage();

    JOptionPane.showMessageDialog(null, "The average for each week is: "+Arrays.toString(average));

}

Answer 1

您正在覆盖 Rainfall 类中的所有成员:

public Rainfall(){
    i = 0;
    j = 0;
    rain = new int[][]{};
    average = new int[]{};
    sum = new int[]{}; // this is the problem
}

这样做有什么好处吗？在调用构造函数(作为成员)之前您已经给它们赋值了，那么为什么要覆盖它们呢？

稍后您调用 setRain() 来启动 rain 数组，但 sum 数组仍为空数组