填充数组时出现java.lang.NullPointerException [英] java.lang.NullPointerException when filling array
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问题描述
目标:通过随机数和排序数创建x
大小的数组.
The goal: create array with x
size by random numbers and sort numbers.
Array.java
import java.util.Random;
/**
* Created by cazorla19 on 05.03.16.
*/
public class Array {
int myArray[];
Random rand;
Array() {
}
Array (int x) {
Array myArray[];
myArray = new Array[x];
for (int i=0; i<x; i++) {
myArray[i] = new Array();
}
}
int[] ArrayFill () {
for (int i=0; i<myArray.length; i++) {
int j = rand.nextInt();
myArray[i] = j;
}
return myArray;
}
int[] ArraySort (){
System.out.println ("Here is the Bubble sort!");
for (int i=0; i<myArray.length; i++) {
for (int j=0; j<myArray.length - i - 1; j++) {
if (myArray[j] > myArray[j+1]) {
int temp = myArray[j];
myArray[j] = myArray [j+1];
myArray[j+1] = temp;
}
}
}
return myArray;
}
void ArrayPrint() {
for (int i=0; i<myArray.length; i++) {
System.out.print (myArray[i] + ", ");
}
}
}
ArrayDo.java
ArrayDo.java
/**
* Created by cazorla19 on 05.03.16.
*/
public class ArrayDo extends Array {
public static void main (String args[]) {
int x = 10;
Array labArray = new Array(x);
labArray.ArrayFill();
labArray.ArrayPrint();
labArray.ArraySort();
labArray.ArrayPrint();
}
}
有点例外.
Exception in thread "main" java.lang.NullPointerException
at Array.ArrayFill(Array.java:23)
at ArrayDo.main(ArrayDo.java:10)
那是我尝试使用数组长度的地方.试图解决这个问题[1][2].尽管我在数组构造函数中做了,但我认为我无法从 NULL 更改数组值.有没有人强迫过类似的问题?我知道这应该很容易,但仍然无法意识到哪里出了问题.
That's where I tried to use length of array. Tried to figured out through this issues [1][2]. It's thought I can't change array values from NULL despite of I did in array constructor. Did anyone force with similar issue? I know it should be pretty easy, but still can't realize what's wrong.
推荐答案
初始化下面的值,你应该很高兴!
Initialize the below values and you should be good to go!
int myArray[]=new int[10];
Random rand=new Random();
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