複寫toString這個方法，IDE一般都有自動生成
代碼如下，建構子我用lombok可以無視

import lombok.AllArgsConstructor;

public class TestObj {
    public static void main(String[] args) {
        TextDB t1 = new TextDB("test1",true);
        System.out.println("沒複寫toString:"+t1);
        //沒複寫toString:TestObj$TextDB@77afea7d

        
        TextDBToString t2 = new TextDBToString("test2",true);
        System.out.println("複寫toString:"+t2);
        //複寫toString:TextDBToString{s1='test2', f1=true}
    }


    @AllArgsConstructor
    private static class TextDB {
        private String s1;
        private Boolean f1;
    }

    @AllArgsConstructor
    private static class TextDBToString {
        private String s1;
        private Boolean f1;

        @Override
        public String toString() {
            return "TextDBToString{" +
                    "s1='" + s1 + '\'' +
                    ", f1=" + f1 +
                    '}';
        }
    }
}