如何从二维数组中获取奇数行或偶数行？答案

【问题标题】：How to get odd or even lines from a two-dimensional array?如何从二维数组中获取奇数行或偶数行？
【发布时间】：2021-08-01 08:00:04
【问题描述】：

如何从二维数组中得到奇数行或偶数行？

String myData [][] = {
        {"test1","test1","test1","test1"},
        {"test2","test2","test2","test2"},
        {"test3","test3","test3","test3"},
        {"test4","test4","test4","test4"},
        {"test5","test5","test5","test5"},
        {"test6","test6","test6","test6"}
    };

并将它们写入 1 或 2 个新数组。需要得到：

String oddLines [][] = { 
    {"test1","test1","test1","test1"},
    {"test3","test3","test3","test3"},
    {"test5","test5","test5","test5"}};

String evenLines [][] = { 
    {"test2","test2","test2","test2"},
    {"test4","test4","test4","test4"},
    {"test6","test6","test6","test6"}};

myData 数组大小未知，可能是

【问题讨论】：

标签： java android arrays

【解决方案1】：

我会使用模数。通常在java中，要检查一个数字是偶数还是奇数，你使用模数。如果var 是偶数，则var % 2 == 0 返回。所以你可以像这样使用它：

String myData [][] = {
        {"test1","test1","test1","test1"},
        {"test2","test2","test2","test2"},
        {"test3","test3","test3","test3"},
        {"test4","test4","test4","test4"},
        {"test5","test5","test5","test5"},
        {"test6","test6","test6","test6"}
};
List<String[]> evenLines = new ArrayList<>();
List<String[]> oddLines = new ArrayList<>();
for (int i = 0; i < myData.length; i++) {
  if (i % 2 == 0) evenLines.add(myData[i]);
  else oddLines.add(myData[i]);
}

检查它是否有效：

System.out.print("Even lines:");
evenLines.forEach((s) -> {
    for(String string : s) System.out.print(" " + string);
});
System.out.print("\nOdd lines:");
oddLines.forEach((s) -> {
    for(String string : s) System.out.print(" " + string);
});

输出：

Even lines:  test1 test1 test1 test1 test3 test3 test3 test3 test5 test5 test5 test5
Odd lines: test2 test2 test2 test2 test4 test4 test4 test4 test6 test6 test6 test6

【讨论】：

【解决方案2】：

你可以使用数学。你知道会有一半是偶数，一半是奇数。您可以使用它和循环将值从原始数组复制到新数组。类似的，

String[][] evenLines = new String[myData.length / 2][];
String[][] oddLines = new String[myData.length - evenLines.length][];
for (int i = 0; i < myData.length; i++) {
    oddLines[i / 2] = myData[i];
    if (i + 1 < myData.length) {
        evenLines[i / 2] = myData[i + 1];
        i++;
    }
}
System.out.printf("oddLines: %s%n", Arrays.deepToString(oddLines));
System.out.printf("evenLines: %s%n", Arrays.deepToString(evenLines));

输出

oddLines: [[test1, test1, test1, test1], [test3, test3, test3, test3], [test5, test5, test5, test5]]
evenLines: [[test2, test2, test2, test2], [test4, test4, test4, test4], [test6, test6, test6, test6]]

【讨论】：