5/23/2018 java entertainment with Package conditions.

1/8

$ ENTERTAINMENT WITH PACKAGE $

[GOLDEN TRUTH 1] Two different folders having the same package with a same class.

{That is , if we set the classpath of two different folders having the same package with a same class

in my program/application then which one package will come in my program.}

We have created two different folders c:\f1 and c:\f3 both having the same class Temp1 containing

the same package making command p1. Now our task is to access the class temp1 of package p1

from another drive\dir\folder say from F:\f2 directory.

F:\f2 containing the class Temp2 with package making command p2 & import command of p1

package.

C:\f1 has Temp1.java

package p1;public class Temp1

{

public void show () {System.out.println ("package p1 from folder f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

C:\f3 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 from folder f3") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

F:\f2 has Temp2.java

package p2;

import p1.*;

public class Temp2

{

public static void main (String s [])

{

new Temp1 ().show ();

}}

5/23/2018 java entertainment with Package conditions.

2/8

Dos command prompt work:

C:\f1>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f1>cd..

C:\>cd f3

C:\f3>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f3> set classpath = c:\f1;c:\f3;

C:\f3>cd\

C:\>f:

F:\>cd f2

F:\f2>javac -d . *.java

// compiler go to the classpath it will see two package with same name in f1 & f3 ,but he use first

folder f1 to import package p1 in class Temp2 to create Temp2.class inside package p2

F:\f2>java p2.Temp2

Package p1 from folder f1

F:\f2> set classpath = c:\f3;c:\f1;F:\f2>javac -d. *.java

F:\f2>java p2.Temp2

Package p1 from folder f3

[GOLDEN TRUTH 2] Two different folders having the two different package, but with a same class.

{That is , if we set the classpath of two different folders having the different package with a same

class in my program/application then what will be happen. Means which class will come}

C:\f1 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 from folder C:\ f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}C:\f3 has Temp1.java

package p3;

public class Temp1

{

public void show () {System.out.println ("package p3 from folder C:\ f3") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

5/23/2018 java entertainment with Package conditions.

3/8

F:\f2 has Temp2.java

package p2;

import p1.*;

import p3.*;

public class Temp2

{

public static void main (String s [])

{

new Temp1 ().show ();

}

}

Dos command prompt work:

C:\f1>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f1>cd..

C:\>cd f3C:\f3>javac -d . *.java // compiler will create Temp1.class inside package p3

C:\f3> set classpath = c:\f1;c:\f3;

C:\f3>cd\

C:\>f:

F:\>cd f2

F:\f2>javac -d . *.java

// compiler will generate ambiguous error (reference to Temp1 is ambiguous)

// In this case, we have to qualified the class Temp2 with package name

// change the F:\f2 \ Temp2.java

public static void main (String s [])

{

new p1.Temp1 ().show ();

}

F:\f2>javac -d . *.java

F:\f2>java p2.Temp2

Package p1 from folder C:\ f1

public static void main (String s [])

{

new p3.Temp1 ().show ();}

F:\f2>javac -d . *.java

F:\f2>java p2.Temp2

Package p3 from folder C:\ f3

5/23/2018 java entertainment with Package conditions.

4/8

[GOLDEN TRUTH 3] Two different folder having a same package, but with a different classes.

{That is , if we set the classpath of two different folders having a same package with different class in

my program/application then what will be happen. Means which classes will come}

C:\f1 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 from folder C:\ f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}}

C:\f3 has Temp3.java

package p1;

public class Temp3

{

public void show () {System.out.println ("package p1 from folder C:\ f3") ;}

public static void main (String s [])

{

Temp3 t3 = new Temp3 ();

t3.show ();

}

}

F:\f2 has Temp2.java

package p2;

import p1.*;

public class Temp2

{

public static void main (String s [])

{new Temp1 ().show ();

new Temp3 ().show ();

}

}

Dos command prompt work:

C:\f1>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f1>cd..

C:\>cd f3

C:\f3>javac -d . *.java // compiler will create Temp1.class inside package p3

C:\f3> set classpath = c:\f1;c:\f3;C:\f3>cd\

5/23/2018 java entertainment with Package conditions.

5/8

C:\>f:

F:\>cd f2

F:\f2>javac -d . *.java

F:\f2>java p2.Temp2

Package p1 from folder C:\ f1

Package p1 from folder C:\ f3

[GOLDEN TRUTH 4] Using the class of one package into the class of default package. In this case we

have to never keep any java file parallel to any package

C:\f1 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 from folder C:\ f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

F:\f2 has Temp2.java

import p1.*;

public class Temp2{

public static void main (String s [])

{

new Temp1 ().show ();

}

}

Dos command prompt work:

C:\f1>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f1> set classpath = c:\f1;

F:\f2>javac Temp2.java

// error: cant access Temp1

Hint: remove source file from parallel to package or place source file in any sub dir/subfolder.

F:\f2>javac Temp2.java

F:\f2>java Temp2

Package p1 from folder C:\ f1

==================================================================================

5/23/2018 java entertainment with Package conditions.

6/8

[GOLDEN TRUTH 5] Using the one class into another class which is parallel to it, but another class is

also having a first class from the another package. In this case, priority always go to (local) parallel

class.

i.e. for eg. Using Temp1 into Temp2; Temp2 is parallel to Temp1 & also Temp2 import Temp1 from

another package.

C:\f1 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 of Temp1 from folder C:\ f1") ;}

public static void main (String s [])

{Temp1 t1 = new Temp1 ();

t1.show ();

}

}

F:\f2 has Temp1.java

package p2;

public class Temp1

{

public void show () {System.out.println ("package p2 of Temp1 from folder F:\ f2") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

F:\f2 has Temp2.java

package p2;

import p1.*;

public class Temp2{

public static void main (String s [])

{

new Temp1 ().show ();

}

}

Dos command prompt work:

C:\f1>javac -d . *.java // compiler will create Temp1.class inside package p1

C:\f1> set classpath = c:\f1;

F:\f2>javac -d . *.javaF:\f2>java p2.Temp2

5/23/2018 java entertainment with Package conditions.

7/8

Package p2 of Temp1 from folder F:\ f2

[GOLDEN TRUTH 6] Using the class of one package into the class of another package without setting

the classpath.

C:\f1 has Temp1.java

package p1;

public class Temp1

{

public void show () {System.out.println ("package p1 from folder C:\ f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}

}

F:\f2 has Temp2.java

Package p2;

import p1.*;

public class Temp2

{

public static void main (String s [])

{

new Temp1 ().show ();}

}

Dos command prompt work:

C:\f1>javac -d . *.java

F:\f2> javac -classpath C:\f1; -d . *.java \\ F:\f2>javac -cp C:\f1; -d . *.java

F:\f2> java -classpath C:\f1;F:\f2; p2.Temp2 \\ F:\f2>java -cp C:\f1;F:\f2 ; p2.Temp2

Package p1 from folder C:\ f1

==================================================================================

$ ENTERTAINMENT WITH PACKAGE $

[GOLDEN TRUTH 7] Setting the classpath of any package via programs.C:> set classpath = F:\bhageria;

class SetClasspath

{

public static void main(String s[])

{

String cp = System.getProperty("java.class.path");

System.out.println(cp);

System.setProperty("java.class.path","c:\\f1");

String cp1 = System.getProperty("java.class.path");

System.out.println(cp1);

5/23/2018 java entertainment with Package conditions.

8/8

}

}

Output:

F:\bhageria

C:\\f1

[AMAZING GOLDEN TRUTH 8] Using the class of default package outside this package.

{NOTE} Only default package class can be accessed outside the package via setting the classpath

only with default package, it will not happen in case of any package .

Default -default = allowed

Default --> package = not allowed

C:\f1 has Temp1.java

public class Temp1

{

public void show () {System.out.println ("package p1 from folder C:\ f1") ;}

public static void main (String s [])

{

Temp1 t1 = new Temp1 ();

t1.show ();

}}

F:\f2 has Temp2.java

public class Temp2

{

public static void main (String s [])

{

new Temp1 ().show ();

}

}

C:\f1>javac Temp1.java

C:\f1>set classpath = C:\f1;

F:\f2> javac Temp2.java

F:\f2> java Temp2

Package p1 from folder C:\ f1