Java language coding for computer programming.
```java
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
```
Let's break down the code:
- The program starts with the `public class HelloWorld` line. This defines a class named "HelloWorld". In Java, every executable program must have at least one class definition.
- Inside the class, we have a `main` method declared as `public static void main(String[] args)`. This is the entry point of the program where the execution begins.
- `public` is an access modifier that allows the main method to be called from anywhere.
- `static` means that the main method belongs to the class itself, rather than any specific object of that class.
- `void` specifies that the main method doesn't return any value.
- `String[] args` is the parameter for the main method. It allows command-line arguments to be passed to the program.
- Inside the `main` method, we have a single line of code: `System.out.println("Hello, World!");`. This line prints the message "Hello, World!" to the console.
- `System.out` refers to the standard output stream, and `println` is a method that prints the provided message and adds a newline character at the end.
To run this program, you need to compile the Java source code into bytecode and then execute it. Here are the steps:
1. Save the code in a file named `HelloWorld.java`.
2. Open a command prompt or terminal and navigate to the directory where the file is saved.
3. Compile the code by executing the command `javac HelloWorld.java`. This will generate a bytecode file named `HelloWorld.class`.
4. Run the program by executing the command `java HelloWorld`. The output should be displayed in the console, showing "Hello, World!".
That's a basic example to get you started with Java programming. You can build upon this foundation to create more complex applications and explore various features of the Java language.
Java language provides several commands that are commonly used for various purposes during development and execution of Java programs. Here are some important Java commands:
1. `javac`: The `javac` command is used to compile Java source code files into bytecode. It takes the source file(s) as input and generates corresponding bytecode file(s) with a `.class` extension. For example, to compile a file named `HelloWorld.java`, you would run: `javac HelloWorld.java`.
2. `java`: The `java` command is used to execute Java bytecode. It takes the bytecode file (class file) as input and runs the program. For example, to run a program with the bytecode file `HelloWorld.class`, you would run: `java HelloWorld`.
3. `jar`: The `jar` command is used to create Java Archive (JAR) files. JAR files are collections of multiple Java class files and resources bundled together for distribution or deployment. The `jar` command can create, update, or extract JAR files. For example, to create a JAR file named `myapp.jar` containing all the files in a directory, you would run: `jar cf myapp.jar directoryName`.
4. `javadoc`: The `javadoc` command is used to generate API documentation from Java source code. It reads specially formatted comments (JavaDoc comments) in the source files and generates HTML documentation files. For example, to generate API documentation for all the files in a directory, you would run: `javadoc -d outputDirectory -sourcepath sourceDirectory`.
5. `javap`: The `javap` command is used to disassemble Java bytecode and display information about the classes, methods, and fields in the bytecode file. It can be helpful for understanding the internal structure of compiled Java code. For example, to disassemble the bytecode file `HelloWorld.class`, you would run: `javap -c HelloWorld`.
These are some of the commonly used commands in Java programming. Each command serves a specific purpose and helps in various stages of Java development, from compiling and running programs to creating documentation and analyzing bytecode.
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