java实现数组反转

方式1-找规律

package p155;

/**
 * @author QinYingjie
 * @version 1.0
 */
public class p164 {
//    数组的反转
//    方式1：通过找规律反转
//    要求：把数组的元素内容反转。ArrayReverse
//    arr{11,22,33,44,55,66}
    public static void main(String[] args) {
        int [] arr1 = {11,22,33,44,55,66,77};
        System.out.println("数组反转前：");
        for (int i = 0; i <arr1.length ; i++) {
            System.out.println(arr1[i]);
        }

        for (int i = 0; i <arr1.length/2 ; i++) {
           int temp =arr1[i];
           arr1[i]=arr1[arr1.length-i-1];
           arr1[arr1.length-i-1]=temp;
        }

        System.out.println("数组反转后：");
        for (int i = 0; i <arr1.length ; i++) {
            System.out.println(arr1[i]);
        }

    }
}

package p155;

/**
 * @author QinYingjie
 * @version 1.0
 */
public class p165 {
    public static void main(String[] args) {
//       写在一起，使用i,j逻辑更清晰
        int [] arr1 = {11,22,33,44,55,66,77};
        System.out.println("数组反转前：");
        System.out.println("---------------");
        for (int i = 0; i <arr1.length ; i++) {
            System.out.println(arr1[i]);
        }

//        -------------------------------------------------------------
        for (int i = 0,j=arr1.length-1; i <j ; i++,j--) {
              int temp =arr1[i];
              arr1[i]=arr1[j];
              arr1[j]=temp;
        }

//        --------------------------------------------------------------
        System.out.println("数组反转后: ");
        System.out.println("---------------");
        for (int i = 0; i < arr1.length ; i++) {
            System.out.println(arr1[i]);
        }

    }
}

方式二：逆序遍历

package p155;

/**
 * @author QinYingjie
 * @version 1.0
 */
public class p166 {
    public static void main(String[] args) {
//        数组反转
//    1.先创建一个新的数组 arr2,大小arr.length
//    2.逆序遍历arr，将每个元素拷贝到arr2中
        int [] arr1 = {11,22,33,44,55,66,77};
        int [] arr2 = new int[arr1.length];
        for (int i = arr1.length-1,j=0; i >=0 ; i--,j++) {
            arr2[j]=arr1[i];
        }

        arr1 = arr2;
        System.out.println("逆序后的：");
        for (int i = 0; i <arr1.length ; i++) {
            System.out.println(arr1[i]);
        }
    }
}