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Would it suppose any difference regarding overhead to write an import loading all the types within one package (import java.*); than just a specific type (i.e. import java.lang.ClassLoader)? Would the second one be a more advisable way to use than the other one?
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Wildcard imports tell java compiler to search for class names in the given package. Hence, using wild card imports, the compile-time performance may lower a bit.
Answer. The asterisk(*) sign indicates that all the classes in the imported package can be used in the program.
import is a Java keyword. It declares a Java class to use in the code below the import statement. Once a Java class is declared, then the class name can be used in the code without specifying the package the class belongs to. Use the '*' character to declare all the classes belonging to the package.
There is no performance difference between a specific import and a wildcard import declaration. The information for the classes in imported package is not read in at compile time or run time unless the class is used in the program.
Take a look at the java API, and you'll see many classes and interfaces with the same name in different packages.
For example:
java.lang.reflect.Array java.sql.Array So, if you import java.lang.reflect.* and java.sql.* you'll have a collision on the Array type, and have to fully qualify them in your code.
Importing specific classes instead will save you this hassle.
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