[英]How do I use parts of an old array to create a new one in java?
因此,我需要创建一个新数组,以交换现有数组的第一个和最后一个值。 这是我到目前为止的内容:
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),但是出现了奇怪的运行时错误。 经过七个输入,得到的输出为: 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.
您必须从java.util.Arrays
导入Arrays
尝试这样的事情:
*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;
}
}
您可以使用以下答案在swapArray()方法中合并数组
只交换传递给swapArray()
函数的数组的第一个和最后一个值并返回而不是创建新数组,会容易得多。
类似于以下内容的东西将起作用(并且它不会创建新变量来促进交换):
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;
}
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