如何打印自定义对象？

public class CustomObject {
    private String name;
    private int age;

    // 构造方法、getter和setter方法省略

    @Override
    public String toString() {
        return "CustomObject [name=" + name + ", age=" + age + "]";
    }
}

public class Main {
    public static void main(String[] args) {
        CustomObject obj = new CustomObject("John", 25);
        System.out.println(obj.toString());
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;

public class CustomObject {
    private String name;
    private int age;

    // 构造方法、getter和setter方法省略

    public String toJsonString() {
        try {
            ObjectMapper mapper = new ObjectMapper();
            return mapper.writeValueAsString(this);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

public class Main {
    public static void main(String[] args) {
        CustomObject obj = new CustomObject("John", 25);
        System.out.println(obj.toJsonString());
    }
}

import java.lang.reflect.Field;

public class CustomObject {
    private String name;
    private int age;

    // 构造方法、getter和setter方法省略

    public void printObject() {
        Class<?> clazz = this.getClass();
        Field[] fields = clazz.getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true);
            try {
                System.out.println(field.getName() + ": " + field.get(this));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        CustomObject obj = new CustomObject("John", 25);
        obj.printObject();
    }
}