Java Tutorial
First Program In java
First Program in Java : Java mein “Hello World” program likhne ke liye kuch simple steps hote hain. Yahan aapko ek basic Java program ka example milta hai:
Yeh program ek simple Java class ko darust taur par represent karta hai. Kuch important points:
public class HelloWorld {
public static void main(String[] args) {
// Yahaan "Hello, World!" likhne ke liye System.out.println ka istemal hota hai.
System.out.println("Hello, World!");
}
}
–public class HelloWorld`: Java program ek ya multiple classes mein ho sakta hai. Yahan `HelloWorld` ek public class hai, jiska naam file ke naam ke saath match karna chahiye.
– public static void main(String[] args)`: Har Java program ka execution `main` method se shuru hota hai. Yeh method public, static, aur void hota hai.
– System.out.println(“Hello, World!”);: Yeh ek print statement hai jo “Hello, World!” ko console par print karega.
Is code ko ek Java file mein save karein, jiska naam `HelloWorld.java` ho. Phir aap ise terminal ya command prompt mein compile aur execute kar sakte hain.
Compile karn ke liye terminal mein ye command likhein:
“`bash
javac HelloWorld.java
“`
Execute karn ke liye ye command likhein:
“`bash
java HelloWorld
“`
Agar sab kuch thik se hua toh aapko output mein “Hello, World!” dikhega.
Here we explain all points in Java Program
Chaliye har kirdar (word) ko ek ek karke samjhein:
1. **public:** Yeh ek access modifier hai, jo batata hai ki class ya method kis level se access ho sakta hai. `public` ka istemal yahaan class ke liye kiya gaya hai, iska matlab hai ki ye class kisi bhi dusre class ya file se accessible hai.
2. **class:** Java mein har program ek class ke andar hota hai. Yahaan `HelloWorld` ek class hai.
3. **HelloWorld:** Yeh class ka naam hai. Java mein class ka naam hamesha file ke naam ke saath match karna chahiye, aur file ka extension `.java` hona chahiye.
4. **{ } (Braces):** Yeh curly braces code blocks ko define karte hain. Java mein class body aur method body ko define karne ke liye inka istemal hota hai.
5. **public static void main(String[] args):** Yeh ek special method hai jo har Java program ki execution ko shuru karta hai. Is method ka signature (method declaration) kuch is tarah ka hota hai:
– `public`: Access modifier hai, jo batata hai ki yeh method public level se accessible hai.
– `static`: Static method hai, jo class ke instance ke bina bhi call ho sakta hai.
– `void`: Yeh batata hai ki yeh method koi value nahi return karta.
– `main`: Yeh method ka naam hai, aur iska execution shuru hota hai jab program chalaya jata hai.
– `(String[] args)`: Method ke parameters hote hain, yahan `main` method ek String array (`args`) ko parameter ke roop mein leta hai.
6. **System.out.println(“Hello, World!”);:** Yeh ek print statement hai, jo console par kuch likhne ke liye istemal hota hai.
– `System`: Yeh ek pre-defined class hai Java mein, jiska istemal system-level operations ke liye hota hai.
– `out`: Yeh ek static object hai `System` class ka, jo output stream ko represent karta hai.
– `println`: Yeh ek method hai jo string ya dusre data ko console par print karne ke liye istemal hota hai.
7. “Hello, World!”: Yeh ek string hai jo console par print kiya jayega. Strings ko double quotes mein likha jata hai Java mein.
Toh, yeh ek basic Java program hai jo “Hello, World!” ko console par print karta hai.
