[英]For-loop overwriting array once finished
在下面的代码中,我尝试制作一个数组洗牌器。 这将按照runTimes
的指示多次对字符数组 ( charArray
) 进行洗牌,将这些 arrays 中的每一个存储在二维数组shuffledArrays
中。 问题是当程序完成 for 循环时,由于某种原因,它将所有 arrays 设置为最后添加的。
任何帮助表示赞赏,谢谢。
import java.util.Random;
public class Testing {
public static void main(String[] args) {
char[] charArray = {'a', 'b', 'c', 'd', 'e', 'f'}; //Array to be shuffled
int runTimes = 3; //Amount of shuffled arrays to create
char[][] shuffledArrays = new char[runTimes][charArray.length];;
for (int x = 0; x != runTimes; x++) {
shuffledArrays[x] = shuffleArray(charArray);
System.out.print("IN FOR LOOP: shuffledArrays[" + x + "] = ");
System.out.println(shuffledArrays[x]);
}
System.out.print("OUT OF FOR LOOP: shuffledArrays[0] = ");
System.out.println(shuffledArrays[0]);
System.out.print("OUT OF FOR LOOP: shuffledArrays[1] = ");
System.out.println(shuffledArrays[1]);
System.out.print("OUT OF FOR LOOP: shuffledArrays[2] = ");
System.out.println(shuffledArrays[2]);
}
private static char[] shuffleArray(char[] array) {
Random rand = new Random();
for (int x = 0; x < array.length; x++) {
int randomIndexToSwap = rand.nextInt(array.length);
char temp = array[randomIndexToSwap];
array[randomIndexToSwap] = array[x];
array[x] = temp;
}
return array;
}
}
由于您总是返回SAME数组,因此最后一个数组会影响所有数组。 您需要返回副本或传递副本,例如:
private static char[] shuffleArray(char[] array) {
Random rand = new Random();
for (int x = 0; x < array.length; x++) {
int randomIndexToSwap = rand.nextInt(array.length);
char temp = array[randomIndexToSwap];
array[randomIndexToSwap] = array[x];
array[x] = temp;
}
return Arrays.copyOf(array, array.length);
}
您需要更改数组的副本,而不是更改原始数组,例如
private static char[] shuffleArray(char[] inArray) {
Random rand = new Random();
char[] array = inArray.clone();
for (int x = 0; x < array.length; x++) {
int randomIndexToSwap = rand.nextInt(array.length);
char temp = array[randomIndexToSwap];
array[randomIndexToSwap] = array[x];
array[x] = temp;
}
return array;
}
示例运行:
IN FOR LOOP: shuffledArrays[0] = dcfaeb
IN FOR LOOP: shuffledArrays[1] = edcbaf
IN FOR LOOP: shuffledArrays[2] = bfaced
OUT OF FOR LOOP: shuffledArrays[0] = dcfaeb
OUT OF FOR LOOP: shuffledArrays[1] = edcbaf
OUT OF FOR LOOP: shuffledArrays[2] = bfaced
您观察到同一阵列的三种状态。 for 循环的第一次迭代的System.out.println()
语句打印第一个 state,例如f, b, c, e, a, d
。 然后第二次迭代你再次洗牌相同的数组,例如a, e, b, f, c, d
。 第三次迭代同上。
现在shuffledArrays[0]
、 shuffledArrays[1]
和shuffledArrays[2]
指向同一个数组。
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