如何使用內部類正確實現Java接口？

Question

我有一段代碼將事件寫入日志文件：

Date rightNow = new Date();
File logfile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS), ("MyLogfile" + fileSDF.format(rightNow) + ".txt"));
FileOutputStream fos;
boolean documents_directory_exists = logfile.getParentFile().exists();
boolean documents_directory_created = true;
if(!documents_directory_exists) documents_directory_created = logfile.getParentFile().mkdirs();
if(documents_directory_created){
    try {
        fos = new FileOutputStream(logfile, true);
        fos.write(new LogEntry(timestampSDF.format(rightNow), boolean01, someInt, boolean02).toString().getBytes());
        fos.close();
    } catch (IOException ioe) {
        Log.e(SomeClass.class.getName(), String.format(Locale.US, "%s %s", Constants.DEFAULT_FILE_ERROR_MESSAGE, ioe.getMessage()));
    }
} else {
        Log.e(SomeClass.class.getName(), String.format(Locale.US, "%s %s", Constants.DEFAULT_FILE_ERROR_MESSAGE, "Cannot create the necessary directories."));
}

我在多個地方都有此代碼，所以我想將其粘貼在接口中，以便使代碼更整潔。 所以我創建了這個接口：

public interface LogWriter {
    void writeLog(LogEntry logEntry);
}

其中LogEntry是：

public class LogEntry{
    private String timestamp;
    private boolean booean01;
    private int someInt;
    private boolean boolean02;

    public LogEntry(timestamp, boolean01, someInt, boolean02){
        this.timestamp = timestamp;
        this.boolean01= boolean01;
        this.someInt= someInt;
        this.boolean02= boolean02;
    }

    // Getters and Setters
}

我想保持代碼的整潔，所以我想在接口中執行所有文件I / O，所以我創建了一個內部類：

public interface LogWriter {
    void writeLog(LogEntry logEntry);

    class WriteMeToTheLog {
        LogEntry logEntry;

        private static final SimpleDateFormat fileSDF = new SimpleDateFormat(Constants.ACCESS_LOGFILE_NAME_FORMAT);

        public WriteMeToTheLog(LogEntry logEntry) {
            this.logEntry = logEntry;
        }

        public void write(){
             Date rightNow = new Date();
             File logfile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS), ("MyLogfile" + fileSDF.format(rightNow) + ".txt"));
             FileOutputStream fos;
             boolean documents_directory_exists = logfile.getParentFile().exists();
             boolean documents_directory_created = true;
             if(!documents_directory_exists) documents_directory_created = logfile.getParentFile().mkdirs();
             if(documents_directory_created){
                 try {
                     fos = new FileOutputStream(logfile, true);
                     fos.write(new LogEntry(timestampSDF.format(rightNow), boolean01, someInt, boolean02).toString().getBytes());
                     fos.close();
                 } catch (IOException ioe) {
                     Log.e(SomeClass.class.getName(), String.format(Locale.US, "%s %s", Constants.DEFAULT_FILE_ERROR_MESSAGE, ioe.getMessage()));
                }
            } else {
                Log.e(SomeClass.class.getName(), String.format(Locale.US, "%s %s", Constants.DEFAULT_FILE_ERROR_MESSAGE, "Cannot create the necessary directories."));
            }
        }
    }
}

這是我收到很失落。

在具有原始代碼塊的一個類中，我實現了新接口：

public class OneOfMyClasses extends BaseClass implements LogWriter {
    public myMethod(){
        // This is where I had the original block of code
        // WHAT DO I DO HERE NOW???
    }

    @Override
    public void writeLog(){
        Date rightNow = new Date();
        writeMeToTheLog(new LogEntry(timestampSDF.format(rightNow), boolean01, someInt, boolean02).toString().getBytes());
        writeMeToTheLog.write();
    }
}

如何使用這項新功能？

Answer 1

我想保持代碼的整潔，所以我想在接口中執行所有文件I / O，因此我創建了一個內部類

在接口中聲明一個類不是“干凈的”。
此外，這不是內部類，而是靜態類，因為該類在接口中聲明。
所有這些都是相對直觀的。 該類是一個實現，而接口是一個API。 API聲明實現結構聽起來並不好。

關於您的問題，我認為WriteMeToTheLog （包含您提取的日志記錄邏輯）還必須實現LogWriter因為它看起來像LogWriter實現。
客戶端類應該具有對WriteMeToTheLog的依賴關系，可能是在構造函數中設置的字段，盡管它仍然可以實現LogWritter如果有意義）。

那會給：

class WriteMeToTheLog implements LogWriter { ...}

和：

public class OneOfMyClasses extends BaseClass implements LogWriter {
    private LogWriter logWriter;

    public OneOfMyClasses (LogWriter logWriter){
       this.logWriter = logWriter;
    }

    @Override
    public void writeLog(){
        Date rightNow = new Date();       
        logWriter.write();
    }
}

現在，您可以通過設置依賴關系來實例化客戶端類：

OneOfMyClasses o = new OneOfMyClasses(new WriteMeToTheLog(new LogEntry(timestampSDF.format(rightNow), boolean01, someInt, boolean02).toString().getBytes());