MastFancy

新手Java语法问题：字符转义相关疑问?

Java语法相关，什么情况下需要多打一个""? import java.util.Scanner; import java.util.regex.Pattern; public class Main { public static void main(String[] args) { String str; Scanner sc = new Scanner(System.in); str = sc.nextLine(); int index = str.indexOf('['); int lastIndex = str.lastIndexOf(']'); str = str.substring(index + 1, lastIndex); String s = "1"; System.out.println("str:" + str); if (Pattern.matches(str, s)) System.out.println("str与s匹配成功！"); else System.out.println("str与s匹配失败！"); String str1 = "\\d"; System.out.println("str1:" + str1); if (Pattern.matches(str1, s)) System.out.println("str1与s匹配成功！"); else System.out.println("str1与s匹配成功！"); System.out.println(str1.equals(str)); } } "我的尝试" (https://wmprod.oss-cn-shanghai.aliyuncs.com/c/user/20240930/01f89e98aa8853a84575516bf681c4fc.png)