如果可以安全地从try-with-resource返回InputStream [英] If it safe to return an InputStream from try-with-resource
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问题描述
从try-with-resource语句返回输入流以在调用方消耗掉它之后处理该流的关闭是否安全?
Is it safe to return an input stream from a try-with-resource statement to handle the closing of the stream once the caller has consumed it?
public static InputStream example() throws IOException {
...
try (InputStream is = ...) {
return is;
}
}
推荐答案
它很安全,但是将关闭,因此我认为它不是特别有用...(您无法重新打开关闭的流.)
It's safe, but it will be closed, so I don't think it is particularly useful... (You can't reopen a closed stream.)
请参见以下示例:
public static void main(String[] argv) throws Exception {
System.out.println(example());
}
public static InputStream example() throws IOException {
try (InputStream is = Files.newInputStream(Paths.get("test.txt"))) {
System.out.println(is);
return is;
}
}
输出:
sun.nio.ch.ChannelInputStream@1db9742
sun.nio.ch.ChannelInputStream@1db9742
返回(相同)输入流(按引用相同),但是将关闭.通过将示例修改为:
The (same) input stream is returned (same by reference), but it will be closed. By modifying the example to this:
public static void main(String[] argv) throws Exception {
InputStream is = example();
System.out.println(is + " " + is.available());
}
public static InputStream example() throws IOException {
try (InputStream is = Files.newInputStream(Paths.get("test.txt"))) {
System.out.println(is + " " + is.available());
return is;
}
}
输出:
sun.nio.ch.ChannelInputStream@1db9742 1000000
Exception in thread "main" java.nio.channels.ClosedChannelException
at sun.nio.ch.FileChannelImpl.ensureOpen(FileChannelImpl.java:109)
at sun.nio.ch.FileChannelImpl.size(FileChannelImpl.java:299)
at sun.nio.ch.ChannelInputStream.available(ChannelInputStream.java:116)
at sandbox.app.Main.main(Main.java:13)
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