我有一些类(例如,医院,医生,护士等),我需要编写一个通用类,将一个不同类型的对象附加到文件中。每个类都有一个显示其字段的方法,但是我无法传递此错误“无法解析方法'print'in T”这是代码:
package Service;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
public class WriteFileService<T>
{
private static WriteFileService instance;
private WriteFileService(){}
public static WriteFileService getInstance()
{
return instance;
}
public void appendObject(T object, String fileName)
{
try {
File file = new File(fileName);
// creates the file if it does not exist
if (!file.exists())
file.createNewFile();
FileWriter fw = new FileWriter(file, true); // append mode = true
BufferedWriter bufferedWriter = new BufferedWriter(fw);
object.print(bufferedWriter); //! ERROR: Cannot resolve method 'print' in T
bufferedWriter.flush();
bufferedWriter.close();
}
catch(IOException e)
{
System.out.println("Problem handling the files!");
e.printStackTrace();
}
}
}
关于该方法的任何帮助都将有所帮助
由于类型擦除,您的T在运行时被视为Object,并且Object类中没有print()
方法。您可以添加界面:
public interface Printable {
void print();
}
并让您所有的类都实现它。然后,您需要更改此设置:
public class WriteFileService<T>
至此:
public class WriteFileService<T extends Printable>