java - 使用 [a-z] 正则表达式在 Java 中拆分字符串

Question

我有两个正则表达式:

[a-c] : any character from a-c

[a-z] : any character from a-z

还有一个测试:

public static void main(String[] args) {
    String s = "abcde";
    String[] arr1 = s.split("[a-c]");
    String[] arr2 = s.split("[a-z]");

    System.out.println(arr1.length); //prints 4 : "", "", "", "de"
    System.out.println(arr2.length); //prints 0 
}

为什么第二次 split 会这样？我希望有 6 个空字符串 ""结果的结果。

Answer 1

根据 the documentation of the single-argument String.split :

This method works as if by invoking the two-argument split method with the given expression and a limit argument of zero. Trailing empty strings are therefore not included in the resulting array.

要保留尾随字符串，您可以使用双参数版本，并指定一个负数限制:

    String s = "abcde";
    String[] arr1 = s.split("[a-c]", -1); // ["", "", "", "de"]
    String[] arr2 = s.split("[a-z]", -1); // ["", "", "", "", "", ""]