在java中反转数组

好吧，你把索引和值搞混了.索引应为整数，值应为浮点数.

Note:索引始终从0开始，在length - 1结束.

public class Main {
    public static void main(String[] args) {
        double[] testArray = new double[] {
            3.5, 7.9, 0.0, -7.9, 10.99, 78.9, 66.8, 19.01, 18.9, 99.7
        };
        double[] reversedArray = new double[testArray.length]; // Use length of original

        // Loop through each index
        for (int i = 0; i < testArray.length; i++) {
            reversedArray[i] = testArray[testArray.length - i - 1];
        }

        // Iterate through the values
        for (double value : reversedArray) {
            System.out.println(value);
        }
    }
}

输出

99.7
18.9
19.01
66.8
78.9
10.99
-7.9
0.0
7.9
3.5

或者，您可以通过向后索引来指定反转值，如下所示:

for (int i = testArray.length - 1; i >= 0; i--) {
    reversedArray[testArray.length - i - 1] = testArray[i];
}

如果您想就地交换并且不关心改变原始数组，您可以try 交换.

它将在O(n/2)下运行:

public class Main {
    public static void main(String[] args) {
        double[] testArray = new double[] {
            3.5, 7.9, 0.0, -7.9, 10.99, 78.9, 66.8, 19.01, 18.9, 99.7
        };

        for (int i = 0; i < testArray.length / 2; i++) {
            // Perform a swap
            double tmp = testArray[testArray.length - i - 1];
            testArray[testArray.length - i - 1] = testArray[i];
            testArray[i] = tmp;
        }

        for (double value : testArray) {
            System.out.println(value);
        }
    }
}