What does import java.io* mean?

Question

Options

• AOnly the io class is imported.
• BAll classes in the io package are imported.
• CAll classes whose names start with io are imported.
• DAll classes in the io package and the subpackages of io packages, if any, are imported.

• A
  3% (2)
• B
  2% (1)
• C
  5% (3)
• D
  90% (55)

Explanation

Important note: the provided answer key contains an error. The correct answer is actually B, not D.

In Java, the wildcard import import java.io.* imports all classes and interfaces directly within the java.io package - but it explicitly does not import subpackages. This is a fundamental Java rule: the * wildcard applies only to the named package's direct members, never recursively to nested packages. To import from a subpackage, you'd need a separate import statement (e.g., import java.io.somesub.*).

Why the distractors are wrong:

• A is wrong - io is a package, not a single class; * expands to all classes within it.
• C is wrong - the * wildcard is scoped to a specific package, not a name prefix search across the whole classpath.
• D is wrong - this is the tricky one. Subpackages are never included; each package must be imported explicitly. Many exam takers assume recursive behavior, but Java does not work that way.

Memory tip: Think of a Java package like a single folder - * grabs every file in that one folder, but doesn't descend into subfolders. Subpackages are completely separate namespaces in Java's eyes.

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