Java - 2D主要和可实例化类-错误与循环

Question

我得到了App类和循环的帮助。

我得到的错误是:

线程"main"异常java.lang.ArrayIndexOutOfBoundsException: 0在rainfall.Rainfall.compute参考:

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

at rain . rainfallapp .main参考:

    r.compute();)

C:Users~run.xml:53: Java返回:1BUILD FAILED(总时间:5秒)

Instantiable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);
}
}

应用程序文件:

    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

您正在重写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?在调用构造函数之前(作为成员)已经给了它们值，那么为什么要重写它们呢?

之后调用setRain()，启动rain数组，但sum数组仍然是空数组