java - 反转字符串，代码无法正常工作

Question

我认为我的语法有问题。所以请帮我解决这些语法:

public class Main { 

  public static void main(String arg[]) { 
    String number = "1234";
    System.out.println("original String: " + number);
    String reversed = inPlaceReverse(number);
    System.out.println("reversed String: " + reversed); 
  } 

  public  String inPlaceReverse(final String input) {
    final StringBuilder builder = new StringBuilder(input); 
    int length = builder.length();
    for (int i = 0; i < length / 2; i++) { 
      final char current = builder.charAt(i);
      final int otherEnd = length - i - 1;
      builder.setCharAt(i, .charAt(otherEnd)); // swap 
      builder.setCharAt(otherEnd, current); 
    }
    return builder.toString(); 
  }

}  

反向功能无法正常工作。

Answer 1

StringBuilder 有一个函数可以执行此操作:

StringBuilder.reverse() 您还可以将 .toString() 附加到此调用以将其恢复为字符串。

https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html#reverse()