Question

我有这个界面

/**
 * Exports data provided by a {@link IDataProvider} as described by {@link IExportableColumn}s. This interface is used by
 * {@link ExportToolbar} to provide the export functionality.
 *
 * @author Jesse Long
 * @see ExportToolbar
 * @see IExportableColumn
 */
public interface IDataExporter
    extends IClusterable
{
    ...
    /**
     * Exports the data provided by the {@link IDataProvider} to the {@link OutputStream}.
     *
     * @param <T>
     *      The type of each row of data provided by the {@link IDataProvider}.
     * @param dataProvider
     *      The {@link IDataProvider} from which to retrieve the data.
     * @param columns
     *      The {@link IExportableColumn} to use to describe the data.
     * @param outputStream
     *      The {@link OutputStream} to which to write the exported data.
     * @throws IOException If an error occurs.
     */
    <T> void exportData(IDataProvider<T> dataProvider, List<IExportableColumn<T, ?, ?>> columns, OutputStream outputStream)
        throws IOException;
}

在类中以某种方式实现此接口我可以将T键入特定的内容，我想确保T实现另一个接口吗？

Answer 1

<T extends MyRequisiteType> void exportData(IDataProvider<T> dataProvider, List<IExportableColumn<T,?,?>> columns, OutputStream outputStream) throws IOException;

为什么IExportableColumn<T,?,?>中的2个无界类型参数？当我在应用程序代码中看到这一点时，我总是觉得我错过了一些东西。

你也可以使整个界面参数化，但从我看到的参数数量需要相当大。至少3。

Answer 2

如果您总是想强制T实现某个界面，请使用

<T extends Thing> void exportData(. . .)

如果只想在实现类中限制T，可以使整个接口通用（而不仅仅是方法）。无论如何，这可能是一个好主意：

/**
 * Exports data provided by a {@link IDataProvider} as described by {@link IExportableColumn}s. This interface is used by
 * {@link ExportToolbar} to provide the export functionality.
 * @param <T>
 *      The type of each row of data provided by the {@link IDataProvider}.
 *
 * @author Jesse Long
 * @see ExportToolbar
 * @see IExportableColumn
 */

public interface<T> IDataExporter extends IClusterable
{
    ...
    /**
     * Exports the data provided by the {@link IDataProvider} to the {@link OutputStream}.
     *
     * @param dataProvider
     *      The {@link IDataProvider} from which to retrieve the data.
     * @param columns
     *      The {@link IExportableColumn} to use to describe the data.
     * @param outputStream
     *      The {@link OutputStream} to which to write the exported data.
     * @throws IOException If an error occurs.
     */
    void exportData(IDataProvider<T> dataProvider, List<IExportableColumn<T, ?, ?>> columns, OutputStream outputStream)
        throws IOException;
}

然后你可以在实现类声明中绑定T：

public class MyClass implements IDataExporter<MyRowType> { . . . }

只键入接口方法

2 个答案: