如何在Java中每隔一次更改符号("+“"-")

public class ChangeSymbol {
    public static void main(String[] args) {
        String str = "Hello World";
        StringBuilder result = new StringBuilder();

        boolean changeSymbol = false; // 初始时不更改符号

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);

            if (Character.isLetter(c)) {
                if (changeSymbol) {
                    result.append(Character.toLowerCase(c)); // 更改为小写字母
                } else {
                    result.append(Character.toUpperCase(c)); // 不更改符号，保持原样
                }
                changeSymbol = !changeSymbol; // 每次循环更改符号的状态
            } else {
                result.append(c); // 非字母字符保持原样
            }
        }

        System.out.println(result.toString());
    }
}