<hr />
<h2 id="heading-what-is-java">What is java ?</h2>
<p>Java is a high-level, object-oriented programming language originally developed by Sun Microsystems and released in 1995. It is designed to be platform-independent, meaning that Java programs can run on any device that has a Java Virtual Machine (JVM) installed, regardless of the underlying hardware and operating system.</p>
<hr />
<ul>
<li><p>JVM (Java Virtual Machine): Executes Java bytecode on different platforms.</p>
</li>
<li><p>JRE (Java Runtime Environment): Includes the JVM and libraries for running Java applications.</p>
</li>
<li><p>JDK (Java Development Kit): Full toolkit for Java development, including JRE, compiler, and tools.</p>
</li>
</ul>
<hr />
<h2 id="heading-hello-world-program"><code>hello world</code> Program</h2>
<pre><code class="lang-java">
<span class="hljs-keyword">public</span> <span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">HelloWorld</span> </span>{
    <span class="hljs-function"><span class="hljs-keyword">public</span> <span class="hljs-keyword">static</span> <span class="hljs-keyword">void</span> <span class="hljs-title">main</span> <span class="hljs-params">(String [] args)</span></span>{
        System.out.println(<span class="hljs-string">"Hello World"</span>);
    }
}
</code></pre>
<hr />
<h2 id="heading-variables-in-java">Variables In Java</h2>
<p>Variable is just a container which stores data.</p>
<h3 id="heading-primitive-data-types">Primitive Data Types</h3>
<ol>
<li><p>Integer</p>
<ol>
<li><p>byte</p>
</li>
<li><p>short</p>
</li>
<li><p>int</p>
</li>
<li><p>long</p>
</li>
</ol>
</li>
<li><p>Float</p>
<ol>
<li><p>float</p>
</li>
<li><p>double</p>
</li>
</ol>
</li>
<li><p>Characters</p>
</li>
<li><p>Boolean</p>
</li>
</ol>
<h3 id="heading-size-of-the-data-types">Size of the data types</h3>
<div class="hn-table">
<table>
<thead>
<tr>
<td>Data Type</td><td>Size (in bits)</td><td>Highest Value</td></tr>
</thead>
<tbody>
<tr>
<td>byte</td><td>8</td><td>127</td></tr>
<tr>
<td>short</td><td>16</td><td>32,767</td></tr>
<tr>
<td>int</td><td>32</td><td>2,147,483,647</td></tr>
<tr>
<td>long</td><td>64</td><td>9,223,372,036,854,775,807</td></tr>
<tr>
<td>float</td><td>32</td><td>Approximately 3.4E38</td></tr>
<tr>
<td>double</td><td>64</td><td>Approximately 1.7E308</td></tr>
<tr>
<td>char</td><td>8</td><td>65,535 (represents ' ' in Unicode)</td></tr>
<tr>
<td>boolean</td><td>-</td><td>true or false</td></tr>
</tbody>
</table>
</div>

---

## What is java ?

Java is a high-level, object-oriented programming language originally developed by Sun Microsystems and released in 1995. It is designed to be platform-independent, meaning that Java programs can run on any device that has a Java Virtual Machine (JVM) installed, regardless of the underlying hardware and operating system.

---

* JVM (Java Virtual Machine): Executes Java bytecode on different platforms.
    
* JRE (Java Runtime Environment): Includes the JVM and libraries for running Java applications.
    
* JDK (Java Development Kit): Full toolkit for Java development, including JRE, compiler, and tools.
    

---

## `hello world` Program

```java

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

---

## Variables In Java

Variable is just a container which stores data.

### Primitive Data Types

1. Integer
    
    1. byte
        
    2. short
        
    3. int
        
    4. long
        
2. Float
    
    1. float
        
    2. double
        
3. Characters
    
4. Boolean
    

### Size of the data types

| Data Type | Size (in bits) | Highest Value |
| --- | --- | --- |
| byte | 8 | 127 |
| short | 16 | 32,767 |
| int | 32 | 2,147,483,647 |
| long | 64 | 9,223,372,036,854,775,807 |
| float | 32 | Approximately 3.4E38 |
| double | 64 | Approximately 1.7E308 |
| char | 8 | 65,535 (represents ' ' in Unicode) |
| boolean | \- | true or false |

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Table of contents

What is java ?

`hello world` Program

Variables In Java

Primitive Data Types

Size of the data types

Data Type	Size (in bits)	Highest Value
byte	8	127
short	16	32,767
int	32	2,147,483,647
long	64	9,223,372,036,854,775,807
float	32	Approximately 3.4E38
double	64	Approximately 1.7E308
char	8	65,535 (represents ' ' in Unicode)
boolean	-	true or false