What is a good use case for static import of methods?

Question

This is from Sun's guide when they released the feature (emphasis in original):

So when should you use static import? Very sparingly! Only use it when you'd otherwise be tempted to declare local copies of constants, or to abuse inheritance (the Constant Interface Antipattern). ... If you overuse the static import feature, it can make your program unreadable and unmaintainable, polluting its namespace with all the static members you import. Readers of your code (including you, a few months after you wrote it) will not know which class a static member comes from. Importing all of the static members from a class can be particularly harmful to readability; if you need only one or two members, import them individually.

(https://docs.oracle.com/javase/8/docs/technotes/guides/language/static-import.html)

There are two parts I want to call out specifically:

• Use static imports only when you were tempted to "abuse inheritance". In this case, would you have been tempted to have BusinessObject extend some.package.DA? If so, static imports may be a cleaner way of handling this. If you never would have dreamed of extending some.package.DA, then this is probably a poor use of static imports. Don't use it just to save a few characters when typing.
• Import individual members. Say import static some.package.DA.save instead of DA.*. That will make it much easier to find where this imported method is coming from.

Personally, I have used this language feature very rarely, and almost always only with constants or enums, never with methods. The trade-off, for me, is almost never worth it.

Another reasonable use for static imports is with JUnit 4. In earlier versions of JUnit methods like assertEquals and fail were inherited since the test class extended junit.framework.TestCase.

// old way
import junit.framework.TestCase;

public class MyTestClass extends TestCase {
    public void myMethodTest() {
        assertEquals("foo", "bar");
    }
}

In JUnit 4, test classes no longer need to extend TestCase and can instead use annotations. You can then statically import the assert methods from org.junit.Assert:

// new way
import static org.junit.Assert.assertEquals;

public class MyTestClass {
    @Test public void myMethodTest() {
        assertEquals("foo", "bar");
        // instead of
        Assert.assertEquals("foo", "bar");
    }
}

JUnit documents using it this way.

Effective Java, Second Edition, at the end of Item 19 notes that you can use static imports if you find yourself heavily using constants from a utility class. I think this principle would apply to static imports of both constants and methods.

import static com.example.UtilityClassWithFrequentlyUsedMethods.myMethod;

public class MyClass {
    public void doSomething() {
        int foo = UtilityClassWithFrequentlyUsedMethods.myMethod();
        // Can be written less verbosely as
        int bar = myMethod();
    }
}

This has advantages and disadvantages. It makes the code a bit more readable at the expense of losing some immediate information about where the method is defined. However, a good IDE will let you go to the definition, so this isn't much of an issue.

You should still use this sparingly, and only if you find yourself using things from the imported file many, many times.

Edit: Updated to be more specific to methods, as that's what this question is referring to. The principle applies regardless of what's being imported (constants or methods).

I think static import is really useful to remove redundant class names when using utils classes like Arrays and Assertions.

Not sure why but Ross skipped out the last sentence that mentions this in the documentation he is referencing.

Used appropriately, static import can make your program more readable, by removing the boilerplate of repetition of class names.

Basically copied from this blog: https://medium.com/alphadev-thoughts/static-imports-are-great-but-underused-e805ba9b279f

So for example:

Assertions in tests

This is the most obvious case which I think we all agree on

Assertions.assertThat(1).isEqualTo(2);

// Use static import instead
assertThat(1).isEqualTo(2);

Utils classes and enums

The class name can be removed in many cases when using utils classes making the code easier to read

List<Integer> numbers = Arrays.asList(1, 2, 3);

// asList method name is enough information
List<Integer> numbers = asList(1, 2, 3);

java.time package has a few cases where it should be used

// Get next Friday from now, quite annoying to read
LocalDate.now().with(TemporalAdjusters.next(DayOfWeek.FRIDAY));

// More concise and easier to read
LocalDate.now().with(next(FRIDAY));

Example of when NOT to use

// Ok this is an Optional
Optional.of("hello world");

// I have no idea what this is 
of("hello world");

I agree that they can be problematic from a readability perspective and should be used sparingly. But when using a common static method they can actually increase readability. For example, in a JUnit test class, methods like assertEquals are obvious where they come from. Similarly for methods from java.lang.Math.