Java如何从另一个类中提取字段的值

Question

我试图从另一个只读类获取所有字段和值，并将它们写入一个文件，如何获取字段的值

该类是只读的，没有getter：

  public class colorConstants {
    public static final String BLUE = "blue";
    public static final String RED = "red";
    public static final String YELLOW = "yellow";
    ...
    
    public colorConstants() {}
  }

在另一类中：

Field[] fields = colorConstants.class.getFields();
for(Field : fields) {
  String fieldName = fieldName;
  
  //how to get the value of each field
  String value = fieldName.get()?
}

Answer 1

你可以这样做：

import java.lang.reflect.Field;

import static java.lang.reflect.Modifier.STATIC;

public class Example {
    public static class colorConstants {
        public static final String BLUE = "blue";
        public static final String RED = "red";
        public static final String YELLOW = "yellow";
        public String blah;

        public colorConstants() {}
    }

    public static void main(String[] args) throws IllegalAccessException {
        Field[] fields = colorConstants.class.getFields();
        for (Field field : fields) {

            if ((field.getModifiers() & STATIC) != 0) {
                String value = (String) field.get(null);
                System.out.println(value);
            } else {
                System.out.println("Ignoring non-static field " + field.getName());
            }
        }
    }
}

我改进了样式，将colorConstants改为ColorConstants，因为类名应该以大写字母开头，并将Field改为field