Question

据我所知，Java 7的抑制异常功能是一种自动功能。换句话说，在6中最终块中发生的异常会自动被抑制，有利于在资源分配时发生的异常。

因此，在这个示例中，a）打开资源和b）关闭资源或c）可能两者都可能出错。

据我了解，Java 7将抛出在打开时发生的异常，我们可以要求它们向我们提供抑制异常，这些异常发生在其他地方。

    try (BufferedReader inputReader = Files
            .newBufferedReader(Paths.get(new URI(
                    "file:///Users/me/Desktop/readme.txt")), Charset
                    .defaultCharset())) {
        String inputLine;
        while ((inputLine = inputReader.readLine()) != null) {
            System.out.println(inputLine);
        }
    }

问题是......程序员可以决定什么被压制？毕竟，public addSuppressed()就在那里。

请提供示例和用例。

Answer 1

这不是任意的 - 被抑制的异常会掩盖导致try块失败的主要异常 - 并且是finally块中的异常。此功能可确保您获得所有整个构造中抛出的异常，但您捕获的异常将更重要。

你无法选择被压制的东西。当然，方法就在那里，否则整个事情都无法奏效。如果您愿意，可以编写自己的异常处理代码并自由使用addSuppressed。

Answer 2

为什么要回复新帖：

更多澄清（至少我需要他们一次阅读，特别是在catch方面）
添加了代码
为addSuppressed用法（catch）

案例逐案：

旧try - catch - finally（或try - finally）将禁止除finally阻止之外的所有异常。此外， nothing 将在抑制例外列表中，如果您触摸它，无论是否被抑制。
try - 有资源 - finally会传播try例外，其中finally一个被列入抑制列表。
try -...- catch - finally的工作方式类似。如果catch抛出，则会抑制try异常使其丢失，除非您手动使用addSupressed()捕获异常（将原始异常与新抛出异常绑定）。我相信这是最后一段接受的答案。

public class WhichIsSupressedTryCatchOrFinally {



public static void main(String[] args) {
    try {
//            tryOrFinally(); // throws finally, try one is lost
//            tryCatchOrFinally(); // as above, no suppression info

//            tryWithResourcesOrFinally(); // throws try, adds finally one to it though automatically
        tryWithResourcesCatchOrFinallyCatchThrows();
        tryWithResourcesCatchOrFinallyByHand(); // throws catch, but adding "by hand" try, adds finally also
    } catch (Exception e) {
        e.printStackTrace();
        // System.out.println(Arrays.toString(e.getSuppressed())); -> not needed!
    }
}

static class AResource implements AutoCloseable {

    @Override
    public void close() throws NumberFormatException {
        throw new NumberFormatException("did not see that one coming, did'ya?");
    }
}
private static void tryWithResourcesOrFinally() throws FileNotFoundException {
    try (AResource a = new AResource()) {
        throw new FileNotFoundException("try");
    }
}

private static void tryWithResourcesCatchOrFinallyCatchThrows() throws Exception {
    try (AResource a = new AResource()){
        throw new IOException("try");
    } catch (Exception e) {
        throw new NoSuchElementException("catch");
    }
}

private static void tryWithResourcesCatchOrFinallyByHand() throws Exception {
    try (AResource a = new AResource()){
        throw new IOException("try");
    } catch (Exception e) {
        NoSuchElementException aCatch = new NoSuchElementException("catch");
        aCatch.addSuppressed(e);
        throw aCatch;
    }
}

private static void tryOrFinally() throws Exception {
    try {
        throw new IOException("try");
    } finally {
        throw new Exception("finally");
    }
}

private static void tryCatchOrFinally() throws Exception {
    try {
        throw new IOException("try");
    } catch (Exception e) {
        throw new NoSuchElementException("catch");
    } finally {
        throw new Exception("finally");
    }
}

public static void main(String[] args) { try { // tryOrFinally(); // throws finally, try one is lost // tryCatchOrFinally(); // as above, no suppression info // tryWithResourcesOrFinally(); // throws try, adds finally one to it though automatically tryWithResourcesCatchOrFinallyCatchThrows(); tryWithResourcesCatchOrFinallyByHand(); // throws catch, but adding "by hand" try, adds finally also } catch (Exception e) { e.printStackTrace(); // System.out.println(Arrays.toString(e.getSuppressed())); -> not needed! } } static class AResource implements AutoCloseable { @Override public void close() throws NumberFormatException { throw new NumberFormatException("did not see that one coming, did'ya?"); } } private static void tryWithResourcesOrFinally() throws FileNotFoundException { try (AResource a = new AResource()) { throw new FileNotFoundException("try"); } } private static void tryWithResourcesCatchOrFinallyCatchThrows() throws Exception { try (AResource a = new AResource()){ throw new IOException("try"); } catch (Exception e) { throw new NoSuchElementException("catch"); } } private static void tryWithResourcesCatchOrFinallyByHand() throws Exception { try (AResource a = new AResource()){ throw new IOException("try"); } catch (Exception e) { NoSuchElementException aCatch = new NoSuchElementException("catch"); aCatch.addSuppressed(e); throw aCatch; } } private static void tryOrFinally() throws Exception { try { throw new IOException("try"); } finally { throw new Exception("finally"); } } private static void tryCatchOrFinally() throws Exception { try { throw new IOException("try"); } catch (Exception e) { throw new NoSuchElementException("catch"); } finally { throw new Exception("finally"); } }

所以，你没有选择被压制的东西，而 } 是为了让堆栈痕迹更加完整。

输出：

尝试 - 捕获 - 最后，捕获抛出中断执行：
尝试 - 捕获 - 最后，所有抛出，捕获throwable添加尝试异常，已经最终捆绑在

谁决定哪些例外被抑制？

2 个答案: