replace 将替换一个字母的所有实例.您需要做的就是使用 substring():

replace will replace all instances of a letter. All you need to do is use substring():

public String method(String str) {
    if (str != null && str.length() > 0 && str.charAt(str.length() - 1) == 'x') {
        str = str.substring(0, str.length() - 1);
    }
    return str;
}