public static void main4(String[] args) {
        //length()方法
        String r = "woyaojindachang";
        int length = r.length();
        System.out.println(length);
    }

public static void main(String[] args) {
        //equals方法
        String r = "woyaojindachang";
        if(r.equals("woyaojindachang")) {
            System.out.println("字符串相等");
        } else {
            System.out.println("字符串不同");
        }
    }

public static void main(String[] args) {
        //charAt
        String s = "woyaojindachang";
        char s1 = s.charAt(5);
        System.out.println(s1);
    }

public static void main(String[] args) {
        //indexOf
        String s = "woyaojindachang";
        int location = s.indexOf("j");
        System.out.println(location);
    }

public static void main(String[] args) {
        //trim
        String s = " wo ";
        String s1 = s.trim();
        System.out.println(s1);
    }

public static void main(String[] args) {
        //compareTo
        String s = "woyaojindacahng";
        int s1 = s.compareTo("woyao");
        System.out.println(s1);
    }

  public static void main(String[] args) {
        //toLowerCase
        String s = "WOYAOJINDACHANG";
        String s1 = s.toLowerCase();
        System.out.println(s1);
    }

public static void main(String[] args) {
        //toUpperCase
        String s = "woyaojindachang";
        String s1 = s.toUpperCase();
        System.out.println(s1);
    }

public static void main(String[] args) {
        //replace的使用
        System.out.println("將日期中的-替換為.");
        String date = "2022-07-30";
        System.out.println("替換前: "+date);
        String replace = date.replace("-",".");
        System.out.println("替換后: "+replace);
    }

public static void main(String[] args) {
        //substring
        String s = "woyaojindachang";
        String s1 = s.substring(5);
        System.out.println(s1);
    }

public static void main(String[] args) {
        //substring字符串截取
        String testDate = "20220730";
        String year = testDate.substring(0,4);
        System.out.println(year);
        String month = testDate.substring(4,6);
        System.out.println(month);
        String day = testDate.substring(6,8);
        System.out.println(day);
        System.out.println(year+"年"+month+"月"+day+"日");
    }