Question

我要做的是读取一个文件并使用StringBuilder来反转文件内部的一个字符串单词的顺序。我让它在while循环中工作但是当我将它添加到方法时它只打印出原始文件文本。

这是有效的代码;

// File being read....
while ((currentString = s.next()) != null) {
    a.insert(0, currentString);
    a.insert(0," ");
}

打印

line. this reads it hope I file. this read will program This

以下代码不起作用;

// File being read....
while ((currentString = s.next()) != null) {
    System.out.print(reverse(currentString));
}

方法

public static StringBuilder reverse(String s){
    StringBuilder a = new StringBuilder();
    a.insert(0, s);
    a.insert(0," ");
}

打印

This program will read this file. I hope it reads this line.

我做错了什么？

Answer 1

每次致电StringBuilder a时，您都会创建新的reverse()。您需要保留对StringBuilder的引用，以便正确地将所有字符串附加到它。

// File being read....
StringBuilder a = new StringBuilder();

while ((currentString = s.next()) != null) {
    reverse(a, currentString);
}

// ...

public static void reverse(StringBuilder a, String currentString) {
    a.insert(0, s);
    a.insert(0," ");
}

Answer 2

您正在创建一个新的StringBuilder并在您阅读每个单词时进行打印。您需要构建字符串，然后在所有读数后打印。如果你想在方法中反转但是读取方法之外的每个单词，那么你可以将当前的StringBuilder提供给你的反向方法，如

StringBuilder total = new StringBuilder();
while ((currentString = s.next()) != null) {
    reverse(total, currentString);
}
System.out.print(currentString);

public static void reverse(StringBuilder total, String s) {
    total.insert(0, s);
    total.insert(0, " ");
}

Java方法撤消算法

2 个答案: