Java 8lambda捕获异常

Question

您不是一直讨厌在Runnable中处理检查异常吗？编写一个方法uncheck，该方法捕获所有已检查的异常并将它们转换为未检查的异常。例如，

new Thread(uncheck(
() -> { System.out.println("Zzz"); Thread.sleep(1000); })).start();
// Look, no catch (InterruptedException)!

提示：定义一个接口runnableex，其run方法可能引发任何异常。然后实施

public static Runnable uncheck(RunnableEx runner)

在uncheck函数中使用lambda表达式。

public interface RunnableEx {
    void run() throws Exception;
}

public class TestUncheck {
    public static Runnable uncheck(RunnableEx r) {
        return new Runnable() {
            @Override
            public void run() {
                try {
                    r.run();
                } catch (Exception e) {
                }
            }
        };
    }

    public static void main(String[] args) {
        new Thread(uncheck(
                () -> {
                    System.out.println("Zzz");
                    Thread.sleep(1000);
                }
        )).start();
    }
}

Answer 1

您的代码未能将选中的异常包装成未选中的异常。此外，它没有遵循使用lambda表达式的提示。更正后的版本是：

public static Runnable uncheck(RunnableEx r) {
    return () -> {
        try {
            r.run();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    };
}

确实有可能进一步改进这一点。由于runnableex接口的全部用途是包装runnable，因此可以将工厂方法放置在接口本身中：

public interface RunnableEx {
    void run() throws Exception;
    public static Runnable uncheck(RunnableEx r) {
        return () -> {
            try {
                r.run();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        };
    }
}

当然，现在您的调用代码必须适应：

public static void main(String[] args) {
    new Thread(RunnableEx.uncheck(
            () -> {
                System.out.println("Zzz");
                Thread.sleep(1000);
            }
    )).start();
}

public interface RunnableEx extends Runnable {
    void runWithException() throws Exception;
    @Override default void run() {
            try {
                runWithException();
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
    }
    public static Runnable uncheck(RunnableEx r) {
        return r;
    }
}

public static void main(String[] args) {
    new Thread( (RunnableEx) () -> {
            System.out.println("Zzz");
            Thread.sleep(1000);
        }
    ).start();
}

public class TestUncheck {
    public static Runnable uncheck(Callable<Void> r) {
        return () -> {
            try { r.call(); }
            catch (Exception e) { throw new RuntimeException(e); }
        };
    }

    public static void main(String[] args) {
        new Thread(uncheck(
                () -> {
                    System.out.println("Zzz");
                    Thread.sleep(1000);
                    return null;
                }
        )).start();
    }
}