Java 8 Method expression is giving compilation error

Question

I am new to Java 8 (Lambda Expression). The following piece of code prints all the directories at the path indicated by the variable "file".

File file = new File("/vssexclude/Test/workspace/Test");

File[] names = file.listFiles(fileName -> fileName.isDirectory());

for (File name : names) {
    System.out.println(name.toString());
}

But, when I try to replace the lambda expression with method expression, eclipse is giving compilation error:

File[] names = file.listFiles(File::isDirectory());

What am I missing?

Answer 1

Remove the parenthesis :

File[] names = file.listFiles(File::isDirectory);

When you want to refer to an instance method of an object of a particular type, the syntax to use is :

ContainingType::methodName

This is described in more details here .