如何修剪字符串中的空格？ [复制]

我正在为 J2ME 应用程序编写此函数，因此我没有一些可用的更高级/现代的 Java 类。我正进入（状态java.lang.ArrayIndexOutOfBoundsException关于这一点。所以，显然它不喜欢我初始化的方式newChars数组，或者我在调用时没有正确执行某些操作System.arraycopy.

/*
 * remove any leading and trailing spaces
 */
public static String trim(String str) {
    char[] chars = str.toCharArray();
    int len = chars.length;
    // leading
    while ( (len > 0 ) && ( chars[0] == ' ' ) ) {
        char[] newChars = new char[] {}; // initialize empty array
        System.arraycopy(chars, 1, newChars, 0, len - 1);
        chars = newChars;
        len = chars.length;
    }
    // TODO: trailing
    return chars.toString();
}

The simple way to trim leading and trailing whitespace is to call String.trim(). With Java 11 and later, you can also use String.strip() which uses a different interpretation of what "white space" means¹.

如果您只想修剪前导和尾随空格（而不是所有前导和尾随空格），有一个 Apache commons 方法称为StringUtils.strip(String, String)可以做到这一点；调用它" "作为第二个参数。

您尝试的代码有许多错误，并且从根本上来说效率很低。如果您真的想自己实现这一点，那么您应该：

1. 计算前导空格字符
2. 计算尾随空格字符
3. 如果任一计数不为零，则调用String.substring(from, end)创建一个包含要保留的字符的新字符串。

This approach avoids copying any characters².

^{1 - The different meanings are explained in the respective javadocs. Alternatively, read the answers to Difference between String trim() and strip() methods in Java 11.}

^{2 - Actually, that depends on the implementation of String. For some implementations there will be no copying, for others a single copy is made. But either is an improvement on your approach, which entails a minimum of 2 copies, and more if there are any characters to trim.}