Forcing Java lambda expressions to capture non-final variables in Java

问题

Is it possible to have a lambda expression capture a variable that is not effectively final?

I know that my code would work perfectly if it could capture them, currently I have to create a new variable that copies the non-final variable I want to pass into a lambda expression.

final SomeClass otherObj;

for(int i = 0; i < 10; i++) {
    int a = i;
    someObject.method(() -> otherObj.process(a, a+1))
}

I'd like to pass in 'i' instead of having to create a new temporary variable.

回答1:

You can try this with java8,

IntStream.range(0, 10).forEach(i ->{
   someObject.method(() -> otherObj.process(i, i+1))
});

回答2:

I used the java.util.concurrent.atomic package.

Here is an example:

        AtomicInteger tifCount = new AtomicInteger(0);
        try(DirectoryStream<Path> ds = Files.newDirectoryStream(Paths.get("C:\\ImageStorage")) {
            ds.forEach(path -> {
                if (FileSystems.getDefault().getPathMatcher("glob:**.tif").matches(path)) {
                    tifCount.incrementAndGet();
                }
            });
        }

来源：https://stackoverflow.com/questions/31403049/forcing-java-lambda-expressions-to-capture-non-final-variables-in-java