将用户输入字符串转换为大写Java

String input = "hello world";
String upperCase = input.toUpperCase();
System.out.println(upperCase);  // 输出 "HELLO WORLD"

String input = "hello world";
StringBuilder upperCase = new StringBuilder();
upperCase.append(input);
upperCase.toUpperCase();
System.out.println(upperCase.toString());  // 输出 "HELLO WORLD"

String input = "hello World";
String upperCase = input.replaceAll("(?i)[A-Z]", "好大一个");
System.out.println(upperCase);  // 输出 "hello 好大一个 World"