Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
613 views
in Technique[技术] by (71.8m points)

try catch - Why is declaration required in Java's try-with-resource

Java7's try-with-resources is great and all, but I can't wrap my head around why it is required to include the declaration of the resource in the try statement. My gut says the following should be possible:

CloseableResource thing;
try (thing = methodThatCreatesAThingAndDoesSomeSideEffect()) {
    // do some interesting things
}
thing.collectSomeStats();

Alas, this results in a syntax error (cryptically expecting a ;). Moving the type definition/declaration into the try statement works, which of course moves thing into the corresponding scope. I can figure out how to work around this when I want more from my AutoClosable than getting closed, I'm interested in why the compiler requires it like this.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Since Java 9 you can declare and initialize the variable used inside try-with-resources outside the block. The only additional requirement for variable is that it has to be effectively final.
So now it is possible to do:

CloseableResource thing = methodThatCreatesAThingAndDoesSomeSideEffect();
try (thing) {
    // do some interesting things
}
thing.collectSomeStats();

Hope it helps.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...