Java Basic Syntax

Java syntax refers to the rules and guidelines for writing valid Java code. Here are some key syntax rules in Java:

Java is a case-sensitive language. This means that “Hello” and “hello” are considered two different identifiers.
All statements in Java must end with a semicolon (;). This includes variable declarations, assignments, method calls, and control structures.
Blocks of code are enclosed within curly braces ({}) and can be nested within each other.
Java variables must be declared with a specific data type, such as int, double, or String. The data type determines what kind of values the variable can hold.
Java methods are declared with a return type, which indicates the type of value that the method will return.
Java keywords, such as “if,” “while,” “for,” and “switch,” have a specific syntax and cannot be used as variable or method names.
Java comments can be used to add notes and explanations to the code. Single-line comments start with “//” and extend to the end of the line. Multi-line comments start with “/” and end with “/”.

Here is a simple Java program that prints “Hello, World!” to the console:

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

Let’s break it down:

The first line public class HelloWorld declares a new class named HelloWorld. By convention, the name of the class should match the name of the file (i.e., HelloWorld.java).
The second line public static void main(String[] args) declares the main method, which is the entry point for any Java program. It takes an array of strings as input and returns nothing (void).
The third line { starts the body of the main method.
The fourth line System.out.println("Hello, World!"); prints the string “Hello, World!” to the console. The System.out part refers to the standard output stream, and the println method prints a string followed by a newline character.
The fifth line } ends the body of the main method.
The sixth line } ends the class declaration.

To run this program, you can compile the code using the Java compiler (i.e., javac HelloWorld.java) and then run the resulting bytecode using the Java Virtual Machine (i.e., java HelloWorld). The output should be:

Hello, World!

Let’s learn more Java syntax:

Case Sensitivity

Java is a case-sensitive language, which means that the names of variables, methods, classes, and other identifiers should be written in the same case throughout the program.

int count = 5; // valid
int Count = 10; // valid
int CoUnt = 15; // valid
int couNT = 20; // valid
int CouNT = 25; // valid

int COUNT = 30; // valid, but different from the previous examples

Comments

Comments are used to add notes and explanations to the code. In Java, single-line comments start with // and multiline comments start with /* and end with */.

// This is a single-line comment

/*
This is a multiline comment
that spans multiple lines
*/

Data Types

Java has several data types such as int, float, double, boolean, char, etc. that are used to define variables.

int age = 30;
float price = 2.99f;
double salary = 50000.50;
boolean isTrue = true;
char grade = 'A';

Variables

A variable is a name given to a memory location to store a value. In Java, variables must be declared with their data type before they can be used.

int num1 = 10;
int num2 = 20;
int sum = num1 + num2;
System.out.println("Sum = " + sum);

Operators

Java has various operators such as arithmetic operators (+, -, *, /), relational operators (==, !=, >, <, >=, <=), logical operators (&&, ||, !), etc.

int a = 10;
int b = 20;
int c = a + b; // addition operator
int d = a * b; // multiplication operator
boolean isGreater = (a > b); // greater than operator
boolean isNotEqual = (a != b); // not equal operator
boolean isTrue = (a < b) && (b < c); // logical AND operator

Control Statements

Java supports various control statements such as if-else, switch, for loop, while loop, do-while loop, etc. that are used to control the flow of the program.

int num = 10;
if (num % 2 == 0) {
    System.out.println("Even");
} else {
    System.out.println("Odd");
}

switch (num) {
    case 1:
        System.out.println("One");
        break;
    case 2:
        System.out.println("Two");
        break;
    default:
        System.out.println("Other");
        break;
}

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

while (num < 20) {
    System.out.println(num);
    num++;
}

do {
    System.out.println(num);
    num++;
} while (num < 30);

Classes and Objects

In Java, a class is a blueprint for creating objects. Objects are instances of classes that have their own attributes and behaviors.

class Person {
    String name;
    int age;

    void sayHello() {
        System.out.println("Hello, my name is " + name);
    }
}

Person john = new Person();
john.name = "John";
john.age = 30;
john.sayHello();

These are some basic examples of Java syntax.

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