Basic Syntax and Data Types in Java

This guide introduces you to the basic syntax and data types in Java, providing a foundation for writing Java programs.

Java Program Structure

A basic Java program consists of:

1. Package declaration (optional)
2. Import statements (optional)
3. Class definition
4. Main method (for executable programs)

Here's a simple example:

package com.example;
 
import java.util.Scanner;
 
public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

Variables and Data Types

Java is a statically-typed language, which means you must declare a variable's type before using it.

Variable Declaration

The syntax for declaring a variable is:

dataType variableName = value;

For example:

int age = 25;
String name = "John";

Primitive Data Types

Java has eight primitive data types:

1. byte: 8-bit signed two's complement integer byte b = 100;

2. short: 16-bit signed two's complement integer short s = 10000;

3. int: 32-bit signed two's complement integer int i = 100000;

4. long: 64-bit signed two's complement integer long l = 1000000000L;

5. float: 32-bit IEEE 754 floating point float f = 3.14f;

6. double: 64-bit IEEE 754 floating point double d = 3.14159;

7. boolean: true or false boolean isTrue = true;

8. char: 16-bit Unicode character char c = 'A';

Reference Data Types

Reference types are used to store complex objects. The most commonly used reference type is String:

String greeting = "Hello, Java!";

Operators

Java provides various operators for performing operations on variables and values.

Arithmetic Operators

• + (addition)
• - (subtraction)
• * (multiplication)
• / (division)
• % (modulus)

Example:

int a = 10;
int b = 3;
int sum = a + b;  // 13
int difference = a - b;  // 7
int product = a * b;  // 30
int quotient = a / b;  // 3
int remainder = a % b;  // 1

Comparison Operators

• == (equal to)
• != (not equal to)
• > (greater than)
• < (less than)
• >= (greater than or equal to)
• <= (less than or equal to)

Example:

int x = 5;
int y = 8;
boolean isEqual = (x == y);  // false
boolean isGreater = (x > y);  // false

Logical Operators

• && (logical AND)
• || (logical OR)
• ! (logical NOT)

Example:

boolean a = true;
boolean b = false;
boolean result = a && b;  // false
result = a || b;  // true
result = !a;  // false

Control Flow Statements

Java uses control flow statements to determine the order in which statements are executed.

If-Else Statement

int score = 85;
if (score >= 90) {
    System.out.println("Excellent");
} else if (score >= 80) {
    System.out.println("Good");
} else {
    System.out.println("Keep practicing");
}

For Loop

for (int i = 0; i < 5; i++) {
    System.out.println("Iteration: " + i);
}

While Loop

int count = 0;
while (count < 5) {
    System.out.println("Count: " + count);
    count++;
}

Conclusion

This guide covers the basic syntax and data types in Java. Understanding these fundamentals is crucial for writing Java programs. As you progress, you'll build upon these concepts to create more complex and powerful applications.