Compilation and execution of java programs

It is also an IDE-intensive programming language, with tight integration with Eclipse. If you are just starting out learning Java, here is a basic guide to help you start running the Java application from the command prompt in Windows. Create a simple Java program like the one below using Notepad or another text editor. Open the Command Prompt from the Start Menu. Use the cd command to change your working directory to the directory containing your Java program.

JDK 'javac' and 'java' commands are also described. Compiling a source code file needs a Java compiler. The JDK package contains a Java compiler, which can be invoked by the command "javac".

The "javac" command takes source code file names as command line arguments. For example, entering the following command in command window will invoke the "javac" compiler to compile the "Hello. Executing a Java program needs a JVM.

The "java" command takes the name of the starting class as the command argument. For example, the following command:. The "-classpath" option specifies the class path, which contains directories where the JVM will search for the bytecode files of the starting class and other program units when needed.

About This Book. Instead, it involves a two-step execution, first through an OS-independent compiler; and second, in a virtual machine JVM which is custom-built for every operating system.

Step 2: Enter : Enters symbols for the definitions into the symbol table. Step 3: Process annotations: If Requested, processes annotations found in the specified compilation units. Step 4: Attribute : Attributes the Syntax trees. This step includes name resolution, type checking and constant folding. Step 5: Flow : Performs dataflow analysis on the trees from the previous step.

This includes checks for assignments and reachability. To run, the main class file the class that contains the method main is passed to the JVM and then goes through three main stages before the final machine code is executed. All the other classes referenced in the program are loaded through the class loader. A class loader, itself an object, creates a flat namespace of class bodies that are referenced by a string name. You can run the. From the command line it looks like this:.

The -cp classes flag tells the Java Virtual Machine that all your classes are located under the directory called classes. This is also called the "Class Path" hence the abbreviation cp. The name of the class to run is the last argument in the above command - the myfirstapp.

MyJavaApp part. The JVM needs to know the fully qualified class name all packages plus class name to determine where the corresponding. When you run the the class your command line will look similar to this including the output from the Java app :.

Note, the first command should not have a line break in it. I have put that in only to make it easier to read. That is it!