如何在while循环外使用声明数组，但在while循环中初始化数组？

我对你的代码进行了一些简化，并为其提供了“测试”上下文（简单的main）。

我放置了适当的注释，以便你可以更轻松地跟踪代码。

public static void main(String[] args) { System.out.println("if statement not triggered"); invokeMethod(new char[]{'a', 'b', 'c', 'd', 'e'});

System.out.println("if statement triggered");
invokeMethod(new char[]{'a', 'b', 'c', 'd', 'e', '.', 'g'});

}

private static void invokeMethod(char[] cIP) { // a suggestion is to initialize your arrays to default values // (i.e. if statement is not triggered). In this case, I've // initialized them to a empty arrays. char[] d = new char[]{}; char[] c = new char[]{};

// since you are using cIP.length several times, 
// assign it to a variable for easier understanding/usage
int size = cIP.length;
if (size > 6 && size < 16) {
    if (cIP[size - 2] == '.') {
        // You can use this one-liner to set d to one character.
        // Essentially, your code, just merged into one-liner
        d = new char[]{cIP[size - 1]};
        // instead of char-by-char copying in a loop
        // you can use Arrays.copyOf()
        c = Arrays.copyOf(cIP, size - 2);
    }
}

System.out.println(c);
System.out.println(d);

} 此外，c，d和cIP毫无意义的名字。尝试给变量赋予更有意义的名称。