如何在主类中实现交换数组方法？

Question

public class array {
    public int[] Array;

    public array() {
        Array= new int[11];
    }

    public static void swap(int i, int j, int [] array) {
        int temp=array[i];
        array[i]=array[j];
        array[j]=temp;
    }
    ...
}

public class arrayTest {

   public static void main(String  [] args) {
        array theArray = new array();    
        theArray.display(); //display array
   }
   ...
}

I'm thinking something like this : theArray(0,9 arr[]);

Answer 1

Given below is a sample implementation:

class Array {
    public static void swap(int i, int j, int[] array) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }

    /**
     * 
     * Displays elements of the array from the end to the beginning
     */
    public static void display(int[] array) {
        // Use `for (int i =0; i <array.length; i++)` for forward navigation
        for (int i = array.length - 1; i >= 0; i--) {
            System.out.print(array[i] + " ");
        }
        System.out.println();
    }
}

public class ArrayTest {
    public static void main(String[] args) {
        int[] arr = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
        Array.display(arr);
        Array.swap(0, 9, arr);
        Array.display(arr);
    }
}

Output:

10 9 8 7 6 5 4 3 2 1 
1 9 8 7 6 5 4 3 2 10 

Notice that the static members are class members ie they are one per class as compared to non- static members which are one per instance. Therefore, static members should be accessed using the class name instead of using an instance eg Array.display as shown above.

Side note (because it won't affect the execution of your program): You should always follow Java naming conventions eg the class, array should be named as Array and the class, arrayTest should be named as ArrayTest . Also, try to avoid a name which has already been used in standard Java library eg you should choose a name other than Array .

[Update]

As promised, posting below a different implementation:

import java.util.Random;

class Array {
    int[] array;

    Array(int size) {
        array = new int[size];
        // Initialise the array with random elements from 0 to 100
        Random random = new Random();
        for (int i = 0; i < size; i++) {
            array[i] = random.nextInt(100);
        }
    }

    public void swap(int i, int j) {
        if (i < 0 || j > array.length - 1) {
            System.out.println("Indices should be in the range of 0 to " + (array.length - 1));
            return;
        }
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }

    /**
     * 
     * Displays elements of the array from the end to the beginning
     */
    public void display() {
        for (int i = array.length - 1; i >= 0; i--) {
            System.out.print(array[i] + " ");
        }
        System.out.println();
    }
}

public class ArrayTest {
    public static void main(String[] args) {
        Array arry = new Array(10);
        arry.display();
        arry.swap(0, 9);
        arry.display();
        arry.swap(0, 11);
    }
}

Output from a sample run:

94 50 5 90 78 33 90 61 64 31 
31 50 5 90 78 33 90 61 64 94 
Indices should be in the range of 0 to 9

Note that these are just a couple of sample implementations. I hope, it will help how you write your own implementation as per your requirement. Feel free to comment in case of any doubt/issue.

Answer 2

无需方法交换只需执行以下操作：

a[i] = a[i]^a[j] ^(a[j]=a[i]);