String 类的常用方法都有那些？

public class Main {
    public static void main(String[] args) {
        String str = "hello world";
        System.out.println("Length: " + str.length()); // 输出：11
        System.out.println("Char at index 1: " + str.charAt(1)); // 输出：e
        System.out.println("Substring: " + str.substring(0, 5)); // 输出：hello
    }
}

public class Main {
    public static void main(String[] args) {
        String str1 = "hello";
        String str2 = "Hello";

        System.out.println("Equals: " + str1.equals(str2)); // false
        System.out.println("Equals Ignore Case: " + str1.equalsIgnoreCase(str2)); // true
        System.out.println("Compare To: " + str1.compareTo(str2)); // 32 (h > H)
    }
}

public class Main {
    public static void main(String[] args) {
        String str = "hello world";

        System.out.println("Index Of: " + str.indexOf("world")); // 输出：6
        System.out.println("Contains: " + str.contains("hello")); // 输出：true
        System.out.println("Starts With: " + str.startsWith("hello")); // 输出：true
        System.out.println("Ends With: " + str.endsWith("world")); // 输出：true
    }
}

public class Main {
    public static void main(String[] args) {
        String str = "  hello world  ";

        System.out.println("Concat: " + str.concat("!!!")); // 输出：  hello world  !!!
        System.out.println("Replace: " + str.replace("world", "Java")); // 输出：  hello Java  
        System.out.println("To Upper Case: " + str.toUpperCase()); // 输出：  HELLO WORLD  
        System.out.println("Trim: " + str.trim()); // 输出：hello world
    }
}

public class Main {
    public static void main(String[] args) {
        String str = "apple,banana,orange";

        String[] fruits = str.split(",");
        for (String fruit : fruits) {
            System.out.println(fruit);
        }

        char[] chars = str.toCharArray();
        for (char c : chars) {
            System.out.print(c + " "); // 输出：a p p l e , b a n a n a , o r a n g e
        }
    }
}

public class Main {
    public static void main(String[] args) {
        String str1 = "";
        String str2 = "   ";

        System.out.println("Is Empty: " + str1.isEmpty()); // 输出：true
        System.out.println("Is Blank: " + str2.isBlank()); // 输出：true (Java 11+)
    }
}