java - 如何使用旧数组的一部分在java中创建一个新数组？

Question

所以我需要创建一个新数组来交换现有数组的第一个和最后一个值。这是我到目前为止所拥有的：

import java.util.Scanner;
import java.util.Arrays;
public class P9_ArrayManipulate
{    public static void main (String[] args)
 {   Scanner in = new Scanner(System.in);
    System.out.println("Please enter seven numbers for an Array.");
    int []array = new int[7];
    int total = 0;
    for (int i = 0; i < 7;i++){
            array[i] = in.nextInt();
    }
    System.out.println("Your reversed array is "+reverseArray(array));
    System.out.println("Your swapped array is "+swapArray(array));
    System.out.println("Your array without even numbers is "+evenArray(array));
    System.out.println("The program has finished calling array methods.");
}
 public static int []reverseArray(int []array)
{   int[] reversed = new int[array.length];
    int i;
    for(i=0; i < array.length; i++)
    {
        reversed[i] = array[(array.length - i -1)];
    }
    return reversed;
}
public static int []swapArray (int []array)
{   
  array[0] += array[array.length-1];
  array[array.length-1] = array[0] - array[array.length-1];
  array[0] -= array[array.length-1];
  return array;
}
public static int []evenArray(int []array)
{   for (int i = 0; i < array.length;i++){
    if (array[i]%2 !=0)
    {array[i] = 0;}
    i++;}
    return array; 
}

}

一切都正确编译（据我所知），但我遇到了一个奇怪的运行时错误。七次输入后，我得到这个作为我的输出： Your reversed array is [I@b4d079 Your swapped array is [I@3644d1 Your array without even numbers is [I@3644d1 The program has finished calling array methods.

Answer 1

你必须从java.util.Arrays导入Arrays

Answer 2

试试这样的：

*编辑：如果必须创建新数组，只需创建 int newarray[] = method(); 而不是 array[]=method();

  import java.util.Scanner;
  public class Array 
 {
public static void main (String[] args)
{   Scanner in = new Scanner(System.in);

System.out.println("Please enter seven numbers for an Array.");
int []array = new int[7];
for (int i = 0; i < 7;i++){
    array[i] = in.nextInt();
}

array = reverseArray(array);
System.out.println("Your reversed array is :");
for (int i = 0; i < array.length; i++) {
    System.out.print(array[i]+" ");
}
System.out.println();

array = swapArray(array);
System.out.println("Your swapped array is :");
for (int i = 0; i < array.length; i++) {
    System.out.print(array[i]+" ");
}
//          System.out.println("Your array without even numbers is "+evenArray(array));
System.out.println();
System.out.println("The program has finished calling array methods.");
}
public static int[] reverseArray(int []array)
{   int left = 0;
int right = array.length-1;
while(left<right){
    int reverse = array[left];
    array[left]=array[right];
    array[right] = reverse;
    left++;
    right--;
}
return array;
}
public static int []swapArray (int []array)
{   
    int help = 0;
    help = array[0];
    array[0] = array[6];
    array[6] = help;

    return array;
  }
 }

Answer 3

您可以使用以下答案在 swapArray() 方法中合并数组

How can I concatenate two arrays in Java?

Answer 4

只交换传入swapArray()函数的数组的第一个和最后一个值并返回它而不是创建一个新数组会容易得多。

类似下面的东西会起作用（并且它不会创建一个新变量来促进交换）：

public static int[] swapArray(int[] array) {
    array[0] += array[array.length-1];
    array[array.length-1] = array[0] - array[array.length-1];
    array[0] -= array[array.length-1];
    return array;
}