introduction.md

Introduction

Java is a statically-typed language, which means that the type of a variable is known at compile-time. Assigning a value to a name is referred to as defining a variable. A variable is defined by explicitly specifying its type.

int explicitVar = 10;

Updating a variable's value is done through the = operator. Here, = does not represent mathematical equality. It simply assigns a value to a variable. Once defined, a variable's type can never change.

int count = 1; // Assign initial value
count = 2;     // Update to new value

// Compiler error when assigning a different type
// count = false;

Java is an object-oriented language and requires all functions to be defined in a class. The class keyword is used to define a class.

class Calculator {
    // ...
}

A function within a class is referred to as a method. Each method can have zero or more parameters. All parameters must be explicitly typed, there is no type inference for parameters. Similarly, the return type must also be made explicit. Values are returned from methods using the return keyword. To allow a method to be called by other classes, the public access modifier must be added.

class Calculator {
    public int add(int x, int y) {
        return x + y;
    }
}

Invoking/calling a method is done by specifying its class and method name and passing arguments for each of the method's parameters.

int sum = new Calculator().add(1, 2);  // here the  "add" method has been called to perform the task of addition 

Scope in Java is defined between the { and } characters.

Java supports two types of comments. Single line comments are preceded by // and multiline comments are inserted between /* and */.