Why doesn t importing java util include Arrays and Lists

Question

I am using java on debian 5     java version  1 6 0 20    Java TM  SE Runtime Environment  build 1 6 0 20-b02    Java HotSpot TM  Client VM  build 16 3-b01  mixed mode  sharing    Why is there a difference between the following   Case 1   import java util      Case 2       import java util    import java util Arrays  import java util List    Why doesnt the first case cover the second case   The code only compiles when I import Arrays and List explicitly   Code   import java util    import java util Arrays  import java util List   public class Test           public static void main  String   args                    List lt Integer gt  i   new ArrayList Arrays asList 1 2 3 4 5 6 7 8 9 10                    List lt Integer gt  j   new ArrayList                    ListIterator lt Integer gt  n   i listIterator i size                      while n hasPrevious                              j add n previous                                        println j                       static void println Object o                    System out println o                      static void print Object o                    System out print o                  The error I get when I comment out the 2nd and 3rd import statements are   nattyp debian   dev java  javac Test java Test java 7  cannot find symbol symbol    method asList int int int int int int int int int int  location  class Arrays                 List lt Integer gt  i   new ArrayList Arrays asList 1 2 3 4 5 6 7 8 9 10                                                            Note  Test java uses unchecked or unsafe operations  Note  Recompile with -Xlint unchecked for details  1 error nattyp debian   dev java

User · Answer

Take a look at this forum http   htmlcoderhelper com why-is-using-a-wild-card-with-a-java-import-statement-bad   Theres a discussion on how using wildcards can lead to conflicts if you add new classes to the packages and if there are two classes with the same name in different packages where only one of them will be imported   Update It gives that warning because your the line should actually be   List lt Integer gt  i   new ArrayList lt Integer gt  Arrays asList 0 1 2 3 4 5 6 7 8 9 10    List lt Integer gt  j   new ArrayList lt Integer gt       You need to specify the type for array list or the compiler will give that warning because it cannot identify that you are using the list in a type safe way

User · Answer

I have just compile it and it compiles fine without the implicit import  probably you re seeing a stale cache or something of your IDE    Have you tried compiling from the command line   I have the exact same version     Probably you re thinking the warning is an error    UPDATE  It looks like you have a Arrays class file in the directory where you re trying to compile   probably created before     That s why the explicit import solves the problem   Try copying your source code to a clean new directory and try again  You ll see there is no error this time   Or  clean up your working directory and remove the Arrays class

User · Answer

The difference between  import java util      and  import java util    import java util List  import java util Arrays    becomes apparent when the code refers to some other List or Arrays  for example  in the same package  or also imported generally   In the first case  the compiler will assume that the Arrays declared in the same package is the one to use  in the latter  since it is declared specifically  the more specific java util Arrays will be used

User · Answer

Case 1  should have worked  I don t see anything wrong  There may be some other problems  I would suggest a clean build

[java] Why doesn't importing java.util.* include Arrays and Lists?

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