防止用户在Java中输入空格

String input = "  user input  ";
String trimmedInput = input.trim();
System.out.println(trimmedInput);  // 输出：user input

String input = "user input with spaces";
String noSpacesInput = input.replaceAll("\\s", "");
System.out.println(noSpacesInput);  // 输出：userinputwithspaces

String input = "user input with spaces";
StringTokenizer tokenizer = new StringTokenizer(input);
StringBuilder sb = new StringBuilder();
while (tokenizer.hasMoreTokens()) {
    sb.append(tokenizer.nextToken());
}
String noSpacesInput = sb.toString();
System.out.println(noSpacesInput);  // 输出：userinputwithspaces