首先，在其他任何事情之前......是的，我知道使用ArrayList会比使用数组容易得多。我明白了，但是对于这个项目，我需要学习如何使用递归来处理数组。
好的，所以在下面的代码中，我输出了数组的所有排列，但除非我将数组的大小设置为用户输入的大小+1，否则我会得到一个ArrayIndexOutOfBounds异常。这会导致数组有一个null值，该值作为空格输出，导致输出问题。
为什么要求我将大小设置为输入的大小加一？我该如何解决这个问题？提前谢谢。
package permutearray;
import java.util.Scanner;
/**
*
* @author Ra'kiir
*/
public class PermuteArray {
public static Scanner keyboard = new Scanner(System.in);
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
System.out.print("How many characters in the permute array: ");
int p = keyboard.nextInt();
char[] permuteArray = new char[p+1];
System.out.print("Enter a line of " + p + " characters: ");
String charString = keyboard.next();
for (int i = 0; i < p; i++) {
permuteArray[i] = charString.charAt(i);
}
permutation(permuteArray, 0, p);
} //End main method
private static void permutation(char[] permuteArray, int firstIndex, int lastIndex) {
if (lastIndex - firstIndex == 1) {
print(permuteArray);
swap(firstIndex, lastIndex, permuteArray);
print(permuteArray);
//restore the order in string array
swap(firstIndex, lastIndex, permuteArray);
} else {
//swap String at firstindex with all the next Strings in the array
for (int i = firstIndex, j = 0; i <= lastIndex; i++, j++) {
swap(firstIndex, firstIndex + j, permuteArray);
//With current initial String(s) find combinations for rest of the strings
permutation(permuteArray, firstIndex + 1, lastIndex);
//restore the order in string array
swap(firstIndex, firstIndex + j, permuteArray);
}
}
} //End swap method
private static void swap(int firstIndex, int lastIndex, char[] permuteArray) {
char temp = permuteArray[lastIndex];
permuteArray[lastIndex] = permuteArray[firstIndex];
permuteArray[firstIndex] = temp;
}
private static void print(char[] permuteArray) {
for (int i = 0; i < permuteArray.length; i++) {
System.out.print(permuteArray[i]);
}
System.out.println();
} //End print method
} //End of Main Class