How to install Java and compile single Java file
Install Java in Ubuntu Operating system
sudo apt install openjdk-11-jdk
Install Java in Centos Operating system
sudo yum install java-11-openjdk
To check Java version
ubuntu@manikandan:~$ java -version
openjdk version "11.0.19" 2023-04-18
OpenJDK Runtime Environment (build 11.0.19+7-post-Ubuntu-0ubuntu122.04.1)
OpenJDK 64-Bit Server VM (build 11.0.19+7-post-Ubuntu-0ubuntu122.04.1, mixed mode, sharing)
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Lets create a sample Java file HelloWorld.java
ubuntu@manikandan:~$ ll
total 4
-rw-rw-r-- 1 ubuntu ubuntu 118 Jun 4 23:48 HelloWorld.java
ubuntu@manikandan:~$ cat HelloWorld.java
class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World!");
}
}
We cannot directly run the Java file, first we have to compile the Java file.
Lets compile the Java file HelloWorld.java
Run the javac FILE_NAME to compile the single Java file
ubuntu@manikandan:~$ javac HelloWorld.java
Once the compilation is success, you will see the HelloWorld.class file
ubuntu@manikandan:~$ ll
total 8
-rw-rw-r-- 1 ubuntu ubuntu 427 Jun 4 23:50 HelloWorld.class
-rw-rw-r-- 1 ubuntu ubuntu 118 Jun 4 23:48 HelloWorld.java
Now type the java HelloWorld to run the java program
ubuntu@manikandan:~$ java HelloWorld
Hello, World!
Why we need to compile the Java code
The Java code written is only understandable by Human’s, computer/machine cannot understand this code. Computer can understand only 0 and 1
So the Java compiler will convert the Java code to machine understandable code
What is compiler ?
-
A compiler is a program that takes a high-level language as input and outputs a low-level language (such as assembly or machine code).
-
It is essentially a computer program that converts programming language code into machine code (human-readable code to a binary 0 and 1 bits language for a computer processor to understand).
-
The computer then executes the machine code in order to complete the task.
Key points of Compiler:
-
Compilers check all types of errors, limits, and ranges.
-
It takes longer to run and also requires more memory.
What is Maven
How to install maven in linux operating system
Ubuntu Operating system
Run the following command to install maven
sudo apt update
sudo apt install maven
Centos Operating system
If Java is not installed, run the following command to install Java
sudo yum install java-11-openjdk
Run the following command to install maven
sudo yum update
sudo yum install maven
To check the version of maven
ubuntu@manikandan:~$ mvn --version
Apache Maven 3.6.3
Maven home: /usr/share/maven
Java version: 11.0.19, vendor: Ubuntu, runtime: /usr/lib/jvm/java-11-openjdk-amd64
Default locale: en, platform encoding: UTF-8
OS name: "linux", version: "5.15.0-1033-oracle", arch: "amd64", family: "unix"