Java development involves using command-line tools to compile and execute programs. The primary commands are javac for compilation and java for execution.

Compiling Java Source Code

Use the javac command too compile Java source files, typically with a .java extension. The basic syntax is:

javac [options] [source_file]

• Options:
  • -d: Specifies the output directory for compiled class files; defaults to the current directory.
  • -g: Generates debugging information for use by debuggers.
  • -classpath: Sets the classpath to locate dependent class files during compilation.
• Source File: The path to the Java source file to be compiled.

Example:

javac -d . GreetingProgram.java

This compiles GreetingProgram.java and places the resulting .class file in the current directory.

Executing Compiled Java Programs

After compilation, run the program with the java command. The basic syntax is:

java [options] [class_name]

• Options:
  • -cp or -classpath: Specifies the classpath to find the class files at runtime.
• Class Name: The name of the class to execute, without the .class extension.

Example:

java GreetingProgram

This executes the GreetingProgram.class file located in the current directory.

Complete Example of Compilation and Execution

Consider a Java source file named GreetingProgram.java with the following content:

public class GreetingProgram {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Steps:

1. Compile:

   javac GreetingProgram.java
   

   This generates a GreetingProgram.class file.

2. Execute:

   java GreetingProgram
   

   This runs the compiled program, outputting Hello, World!.

Handling Multiple Source Files

For programs with multiple interdependent source files, ensure all related .class files are in the same directory or specify the correct classpath using -cp or -classpath.

Example:

javac -d . Application.java Helper.java
java Application

Managing Package Structuers

If Java source files use package structures (e.g., in different directories), correctly specify the classpath during compilation and execution.

Example:

javac -d . com/myapp/Application.java
java -cp . com.myapp.Application