Question

我一直在尝试构建一个while循环来循环遍历字符串，当它包含我正在寻找的'模式'时。字符串是一个局部变量，在while循环上方声明，我无法在while循环中对其进行子串，因此每个连续循环都会查看字符串的下一部分。

如果我能解决这个问题，我将不胜感激

这是代码;只是你有这个想法，在线列表通常作为数组列表输出，例如[阿德里安，鲍勃，巴迪]

                String onlineList = networkInput.nextLine();
                //Declare a local variable for modified online list, that will replace all the strings that contain ", " "[" and "]"
                String modifiedOnlineList = onlineList.replaceAll("\\, ", "\n").replaceAll("\\[", "").replaceAll("\\]", "");
                //Loop the modifiedOnlineList string until it contains "\n"
                while (modifiedOnlineList.contains("\n")) {
                    //A local temporary variable for the first occurence of "\n" in the modifiedOnlineList
                    int tempFirstOccurence = modifiedOnlineList.indexOf("\n");
                    //Obtain the name of the currently looped user
                    String tempOnlineUserName = modifiedOnlineList.substring(0, tempFirstOccurence);
                    //Substring the remaining part of the string.
                    modifiedOnlineList.substring(tempFirstOccurence + 2);
                    System.out.println(modifiedOnlineList);

                }

Answer 1

String在java中是不可变的

 modifiedOnlineList = modifiedOnlineList.substring(tempFirstOccurence + 2);

您必须收到String方法返回的新 substring对象。

 modifiedOnlineList.substring(tempFirstOccurence + 2);
 System.out.println(modifiedOnlineList);   // still old value

当你收到

时

 modifiedOnlineList = modifiedOnlineList.substring(tempFirstOccurence + 2);
 System.out.println(modifiedOnlineList);   // now re assigned to substring value

Answer 2

字符串是不可变的。这意味着substring不会修改字符串本身，而是返回一个新的字符串对象。所以你应该使用：

modifiedOnlineList = modifiedOnlineList.substring(tempFirstOccurence + 2);

Answer 3

modifiedOnlineList.substring（）只返回原始的modifiedOnlineList的子字符串，它不会修改modifiedOnlineList。

Java子串在while循环中的局部变量

3 个答案: