正则表达式在java中将字符串拆分为一半

问题描述

我们需要帮助如何为string.split编写正则表达式，这样我们就可以将字符串分成两半。

we need help how to write the regex for string.split so we can split a string in half.

谢谢。

推荐答案

没有明显的正则表达式模式可以做到这一点。 可能可以使用 String.split 执行此操作，但我只使用 substring 像这样：

There's no obvious regex pattern that would do this. It may be possible to do this with String.split, but I'd just use substring like this:

    String s = "12345678abcdefgh";

    final int mid = s.length() / 2;
    String[] parts = {
        s.substring(0, mid),
        s.substring(mid),
    };

    System.out.println(Arrays.toString(parts));
    // "[12345678, abcdefgh]"

以上将拆分奇数长度字符串 part [1] 一个字符长于 part [0] 。如果您需要反过来，那么只需定义 mid =（s.length（）+ 1）/ 2;

The above would split an odd-length String with part[1] one character longer than part[0]. If you need it the other way around, then simply define mid = (s.length() + 1) / 2;

您还可以执行以下操作将字符串拆分为 N - 部分：

You can also do something like this to split a string into N-parts:

static String[] splitN(String s, final int N) {
    final int base = s.length() / N;
    final int remainder = s.length() % N;

    String[] parts = new String[N];
    for (int i = 0; i < N; i++) {
        int length = base + (i < remainder ? 1 : 0);
        parts[i] = s.substring(0, length);
        s = s.substring(length);
    }
    return parts;
}

然后你可以这样做：

    String s = "123456789";

    System.out.println(Arrays.toString(splitN(s, 2)));
    // "[12345, 6789]"

    System.out.println(Arrays.toString(splitN(s, 3)));
    // "[123, 456, 789]"

    System.out.println(Arrays.toString(splitN(s, 5)));
    // "[12, 34, 56, 78, 9]"

    System.out.println(Arrays.toString(splitN(s, 10)));
    // "[1, 2, 3, 4, 5, 6, 7, 8, 9, ]"

请注意，这有利于早期部分保存额外字符，当部件数量超过字符数时，它也有效。

Note that this favors the earlier parts to hold the extra characters, and it also works when the number of parts is more than the number of characters.

在上面的代码中：

• ？：是条件运算符，也就是三元运算符。


• / 执行整数除法。 1/2 == 0 。


• ％执行整数余数运算。 3％2 == 1 。此外， -1％2 == -1 。

• ?: is the conditional operator, aka the ternary operator.
• / performs integer division. 1 / 2 == 0.
• % performs integer remainder operation. 3 % 2 == 1. Also, -1 % 2 == -1.

• JLS 15.25 Conditional Operator ?:
• JLS 15.17.2 Division Operator /
• JLS 15.17.3 Remainder Operator %

• How does the ternary operator work?
• Why does (360 / 24) / 60 = 0 … in Java

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