importing packages in a class

[nirjari patel]

I have created package1, package2 and package3 under packages folder on my desktop.

I want to import these packages in a new class I am creating. Can I just import these packages in the class with import statement in the beginning or do I need to put these packages in some library or path in order to import it in the class ?

Please let me know, what do I need to do in order to import these packages in class. If it needs to be put in library, how to put it in library or path ?

Thanks

[Kevin Workman]

nirjari patel wrote:Can I just import these packages in the class with import statement in the beginning or do I need to put these packages in some library or path in order to import it in the class ?

What happened when you tried that?

The packages have to be on your classpath.

Recommended reading: Setting the class path

[nirjari patel]

This is the path for packages.
"C:\Users\nirjari\Desktop\packages\package1"
"C:\Users\nirjari\Desktop\packages\package2"
"C:\Users\nirjari\Desktop\packages\package3"

package package1;

class BaseClass {

	public int x = 10;
	private int y = 10;
	protected int z = 10;
	int a = 10; //Implicit Default Access Modifier
	public int getX() {
		return x;
	}
	public void setX(int x) {
		this.x = x;
	}
	private int getY() {
		return y;
	}
	private void setY(int y) {
		this.y = y;
	}
	protected int getZ() {
		return z;
	}
	protected void setZ(int z) {
		this.z = z;
	}
	int getA() {
		return a;
	}
	void setA(int a) {
		this.a = a;
	}
}


public class SubclassInSamePackage extends BaseClass {

	public static void main(String args[]) {
		BaseClass rr = new BaseClass();
		rr.z = 0;
		SubclassInSamePackage subClassObj = new SubclassInSamePackage();
		//Access Modifiers - Public
		System.out.println("Value of x is : " + subClassObj.x);
		subClassObj.setX(20);
		System.out.println("Value of x is : " + subClassObj.x);
		//Access Modifiers - Public
		//    	If we remove the comments it would result in a compilaton
		//    	error as the fields and methods being accessed are private
		/*    	System.out.println("Value of y is : "+subClassObj.y);

		 subClassObj.setY(20);

		 System.out.println("Value of y is : "+subClassObj.y);*/
		//Access Modifiers - Protected
		System.out.println("Value of z is : " + subClassObj.z);
		subClassObj.setZ(30);
		System.out.println("Value of z is : " + subClassObj.z);
		//Access Modifiers - Default
		System.out.println("Value of x is : " + subClassObj.a);
		subClassObj.setA(20);
		System.out.println("Value of x is : " + subClassObj.a);
	}
}

I get following errors when I run code on the cmd line.

C:\Users\nirjari\Desktop\packages\package1>java SubclassInSamePackage
Exception in thread "main" java.lang.NoClassDefFoundError: SubclassInSame
(wrong name: package1/SubclassInSamePackage)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(Unknown Source)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$000(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: SubclassInSamePackage. Program will exit.

Please suggest, whats wrong in here. When I am running class file from the path its located in, why do I need to set classpath ?

Thanks

[Kevin Workman]

Read the link I posted. It explains what the classpath is, why you need to set it, and how you set it.

[Campbell Ritchie]

You ought to be working from the directory one level above the packages. You need to call the classes by their fully-qualified names, eg package1.Foo

And package1, package2, etc are very poor names for packages.

[Audrey Williams]

I'm having the same problem importing a package. I'm actually trying to work through the Beverage/Tea example on page 54 of the SCJP Java 6 Study Guide. I set my classpath directory to the bin folder where I'm saving my code, and I also tried setting the classpath to the directory above the bin folder. I still keep getting the error that the package that I'm trying to import doesn't exist. Can someone PLEASE help me.

[Audrey Williams]

I have just fixed my problem. I'm still new to Java, but it looks like my issues were all environmental. I don't know if this will help anyone else, but below is my solution:

1) at the command prompt I typed: Set JAVA_HOME = C:\Program Files\Java\jdk1.6.0_23
2) also at the command prompt: Set Path = %JAVA_HOME%\bin
3) also at the command prompt: Set CLASSPATH = ".;C:\Java"

I'm not 100% sure why this worked....but it did! I ended up creating a C:\Java\src directory to store my .java files instead of keeping them in the bin directory.

[Campbell Ritchie]

Welcome to the Ranch Audrey Williams
Find the "common problems" page in the Java™ tutorials, where it says to look at §4 of the installation instructions about setting your PATH. Put the Java™ installation you want to use before System32 or similar in the PATH string. You may find out why it worked when you read those resources; if not, ask again.

It is usually a bad idea to set a CLASSPATH permanently; if you keep all your files in your "current directory" and navigate there with the cd command, you can probably dispense with a classpath altogether. Leave your classpath blank and see whether it still works; if you have problems, ask again.

Good idea to create a C:\Java directory. I keep telling newbies to do that, so I am please you worked it out for yourself.

[Christian Joseph]

i believe its on HEAD FIRST JAVA book


you need to run it this way


run > cmd

@cmd

type "javac xxx.java"
then type " java application1.xxxx

heres the link http://www.jarticles.com/package/package_eng.html