How to Compile and Run your first Java Program - NareshIT

Compiling and Running your first Java Program

There are various high-level languages, and Java is one of them. And hence we need to compile the Java Program to certain equivalent low-level code that is understandable and executable by the machine. In this article, we discuss how we can write, compile as well as run a Java program. So, let’s begin our article. And you can contact us for your Java training. Naresh I Technologies is the number one computer training institute in Hyderabad and among the top five computer training institutes in India. Contact us anytime for your Java training. 

The first requirement is the creation of a folder, and then we need to create a Java class, and finally write the Java program. And when we write a Java program, the javac or the Java compiler does the translation of the Java source code, and it translates it to the bytecode, and that is a .class file. The Bytecode happens to be the machine language of the JVM. We also know it as the Java magic code, and the Bytecode's biggest feature is that it is platform-independent. 

The most important step once Java is installed on the system is the setting of the path. We have already discussed previously how we can set the path in Java. However, we are briefing here again.

Since Java 11 the JRE has been dropped and now it comes with the JDK itself. You need to install the JDK. For the installation, you need an oracle account., as otherwise, you will not be able to download the Java.  Now go inside c drive, and then inside Program Files, and then inside the Java folder. You will find the JDK. Don’t go inside the bin. Copy the path till JDK, and then go to the Advanced system settings, and then click the environment variable icon. Now double click on Path in the system variable and add the JDK path over there. If you have a java version older than 11 then copy JDK and JRE path till bin, and paste over here. And finally, click on ok. You are done. Write the Java code in a text editor, and then save the file with a .java extension. 

You can take any Java program. We are taking the simplest of the program and as below.

public class Main

{

public static void main(String args[])

{

String a1 = "Welcome to";

String a2 = "Naresh";

String a3="I Technologies";

String a4 = a1 + " " +a2 +""+a3;

System.out.println(a4);

}

}        

Now you have created the Java program. Now save this program as MyfirstJavaProgran.java. 

For compiling this program, you need to make use of the command prompt and the command you need to use is javac. 

Write the command as below

C://java/javac MyFirstJavaProgram.java

This will run the javac.exe which is the compiler, And the generalized format of the command for compiling the java program is 

javac <file name>.java

Once, you run this code your program will get compiled. 

Run this command from inside the java folder in c drive. It's sometimes inside the Program Files folder within the c drive. Now you will find that on the compilation, the .class file is also generated. You will find this within the working directory with the .java file

While compiling the Java program with the help of the javac tool, the java compiler does the below functions like syntax checking, the addition of extra code, and conversion of the source code into byte code. And that is the creation of the .class file from the .java file.

Extra code gets generated, and you can check the .class file for this. Like if you have not mentioned the extra code before compilation, as an instance, suppose you have not added a constructor. Then the compiler will add a default constructor into the .class file.

Hence, the main task of the java compilation Is the generation of the .class file of the program that is understandable by the machine. And this is platform-independent. 

Java needs each of the classes to be placed in its source file which must be exactly as the class name with java extension.

And when we begin the source code compilation, then each of the classes gets placed within the .class file which has the byte code. Now if you need to compile numerous java files at one time, you can make use of the below command

javac *.java 

This command generates the .class files for all the java files.

And that completes the article on the Java compilation process. Hope you now know how to do the java program compilation and hope it's now clear to you each aspect that we have seen in this article.

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FAQ'S

1. What is a Java Virtual Machine (JVM)?

A Java Virtual Machine (JVM) is a software implementation that executes Java bytecode. It acts as an intermediary between the compiled Java code and the underlying operating system. This allows Java programs to run on any platform with a JVM installed, making Java platform-independent.

2. What are the common IDEs used for Java development?

An Integrated Development Environment (IDE) is a software application that provides comprehensive facilities for software development. Some popular IDEs for Java development include:  

Eclipse: A versatile IDE with a large plugin ecosystem.

IntelliJ IDEA: A powerful IDE known for its intelligent code completion and refactoring tools.

NetBeans: An open-source IDE with a user-friendly interface and a wide range of features.

Visual Studio Code: A lightweight and customizable code editor that can be extended for Java development with plugins.

3. What is a Java Compiler, and what does it do?

A Java compiler is a software tool that translates human-readable Java source code into machine-readable bytecode. This bytecode can be executed on any Java Virtual Machine (JVM), making Java platform-independent.

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