No, each class is assigned to a single package. There is really no need to have one class in more than one package, either; you can use the "import" command in one class to use classes from another package.
Package:- package is collection of related classes and interfaces which can be import in our program. There are different built in packages available in java.Package provide us a facility to create user define packages. Interfaces:- Interface is just like abstract class but the difference is that we can implements any no of interfaces in a single class .It is an alternative solution for multiple inheritance which is not available in java. Once we have implement the interface we can define methods of that interface in our class.
Once you have compiled your Java source files: javac MyClass.java You can run the resulting class file and pass arguments: java MyClass arg0 arg1 arg2
I use JD-GUI to de-compile class files back into their java equivalents. This has saved me once or twice when I lost the source code on a project and I needed to update it.
By calling the class that contains it. To test it in your IDE, use the "run" command on this file. To run it independently (once it is compiled), if your class is called MyClass, run the following command from a command window:java MyClassWhen you run a class, the Java Virtual Machine will automatically look for a method called main(), and run it.
There are many reasons of studying java It is most popular programming language and according to me best language I ever used. Java is a general-purpose, concurrent, class-based, object-oriented language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere"
The main difference between a local class and a nested class is, local class can be used for once of a perticular part where as nested class can be used used anywhere through out the program. You may get clear information regarding Interview Questions at http://www.bigvacancies.com/java-interview-questions/
Java is a platform independent language.After compiling the ".java" file ,that will be converting into the ".class" file,which is a byte code having the capability run on any OS.Basing on the concept byte code java achieving the platform independent,it leads to "Write once run anywhere".
Tools provided in java includes, 1. Jar: Mostly used tool of java, it creates jar archive file(executable file by javaw/java if you have jre installed in your system, lib files to import your classes and reuse). 2. Jarsigner: This utility signs a jar, and can verify a signed jar. 3. Keytool: Tool to create keystore and certificates. 4. servertool: Java IDL server tool. 5. Policytool: Edit and create policy, keystore is required for the same. 6. Javah: Tool to create header file. 7. appletviewer: Tool to view applets. 8. HtmlConverter: Convert applet to html. Common uses: java, javac, javaw, javadoc, javap (get the class structure) etc
You can simply list them with spaces separating each file name: javac class1.java class2.java
Write once, run everywhere
In Java, arrays have a fixed size once they are initialized and cannot be extended. If you need a resizable array, you can use the ArrayList class from the Java Collections Framework, which allows for dynamic resizing. Alternatively, you can create a new array with a larger size and copy the elements from the original array to the new one if you want to extend an existing array.
Classes in Java are organized into packages - a hierarchical structure much like folders and files on a computer. When you use a class in your source code, the compiler needs to know where to look to find those classes. By default, it will search within the current package and in the java.lang package; a path to any other classes must be defined somewhere.There are two ways to do this.The first is to explicitly state it whenever you use the class name. This should only be used when you know you will only use the class name once or twice since it produces such messy code:java.util.ArrayList myList = new java.util.ArrayList();In contrast is the import keyword, which expands the areas Java will search for classes.Adding this line will ensure that any time you refer to an "ArrayList" in your code, the compiler will know to look in the java.util package for it.import java.util.ArrayList;