About import command

[ponvijaya]

Hi all,

We are using import command as

import java.io.*, import java.util.* etc in the program.

Consider i am having a class A.

Is there any difference related to Memory consumptions for class A while writing import command as
import java.util.HashM ap ; rather than
import java.util.*;
in the case import java.util.HashM ap i am importing only the class HashMap where as in the case import java.util.* , i am importing all the classes present in util package.

[r035198x]

Hi all,

We are using import command as

import java.io.*, import java.util.* etc in the program.

Consider i am having a class A.

Is there any difference related to Memory consumptions for class A while writing import command as
import java.util.HashM ap ; rather than
import java.util.*;
in the case import java.util.HashM ap i am importing only the class HashMap where as in the case import java.util.* , i am importing all the classes present in util package.

No there's no difference in memory e.t.c.
Importing a class is different from loading a class. The import is there just to help you type shorter names for classes when refencing them from their packages.

[odefta]

There is not a memory problem.

But importing classes can lead to ambiguities. A class name is ambiguous if it occurs in two packages that are imported by wildcards. For example, suppose a program contains the imports

import java.awt.*;
import java.util.*;

The List class exists in both import statements.
If use List in your program, which List trully will use?

[odefta]

Import only tells the compiler where to look for symbols.

The search for names is very efficient so there is no effective difference between
import java.* or import java.Class

[r035198x]

There is not a memory problem.

But importing classes can lead to ambiguities. A class name is ambiguous if it occurs in two packages that are imported by wildcards. For example, suppose a program contains the imports

import java.awt.*;
import java.util.*;

The List class exists in both import statements.
If use List in your program, which List trully will use?

Yep. The compiler will complain if you try to use a non fully qualified List after those imports. You'd need to prefix the full package name if you want to use ambiguous classes.

[JosAH]

Older versions of javac eagerly imported entire class definitions for every class
in a package that was merely mentioned in your class. The newer versions
simply register the fact that every class in that package should be available for
scrutinizing (loading the class defintion) it by the compiler. In the old days
avoiding the '*' thingy was a compilation speedup.

That is not the case anymore; most if not all IDEs can create single class
import directives for you and it is the recommended way of importing classes
(it reduces the chance of ambiguity in case of class name clashes).

kind regards,

Jos

[r035198x]

Older versions of javac eagerly imported entire class definitions for every class
in a package that was merely mentioned in your class. The newer versions
simply register the fact that every class in that package should be available for
scrutinizing (loading the class defintion) it by the compiler. In the old days
avoiding the '*' thingy was a compilation speedup.

That is not the case anymore; most if not all IDEs can create single class
import directives for you and it is the recommended way of importing classes
(it reduces the chance of ambiguity in case of class name clashes).

kind regards,

Jos

One of the joys of being younger

[JosAH]

One of the joys of being younger

Statement: I'm not old :-P

kind regards,

Jos ;-)

[praveen2gupta]

Hi

import java.io.*,
import java.util.* etc in the program.

Consider i am having a class A.
Is there any difference related to Memory consumptions for class A while writing import command as
import java.util.HashM ap ; rather than
import java.util.*;

import java.io.* is default import statement , you need not to write it. While
in second case There is no difference in Memory consuption. Compiler looks these paths at the time of compilation only.

[r035198x]

Hi

import java.io.*,
import java.util.* etc in the program.

Consider i am having a class A.
Is there any difference related to Memory consumptions for class A while writing import command as
import java.util.HashM ap ; rather than
import java.util.*;

import java.io.* is default import statement , you need not to write it. While
in second case There is no difference in Memory consuption. Compiler looks these paths at the time of compilation only.

I'm not entirely sure what you're talking about here.
What do you mean by " import java.io.* is default import statement , you need not to write it."? If you want to use any classes/interfaces in the io package you have to import the package.