BASIC JAVA PROGRAMMING CONCEPTS IN ECLIPSE Project and Package Creation Start by creating a Java Project in Eclipse When you create a new class make sure it s inside a package to keep your code organized For example package com example myapp public class Main Your code goes here 1 int counter 0 double price 10 99 boolean isEligible true String greeting Hello World Variables and Data Types Declare and initialize variables with appropriate data types Here s an example with different data types in action 2 3 Operators and Expressions Perform calculations using various operators like arithmetic and increment operators to manipulate numbers Quote Practice makes perfect and understanding operators will make you a stronger Java programmer Control Structures Master conditional statements and loops to control program flow Example int age 18 if age 18 else System out println You are an adult System out println You are not an adult yet For loops can iterate through arrays and collections int numbers 1 2 3 4 5 for int i 0 i numbers length i System out println numbers i 4 public static void printHello int times for int i 0 i times i System out println Hello World 5 6 Important Notes Methods Functions Create and use your own custom functions Here s an example method that takes an integer parameter Naming conventions classNames variableNames methodNames Access modifiers public private protected Learn more with additional resources and continue experimenting with code examples to further refine your Java skills As you explore Java programming make sure to have fun and stay positive Believe you can and you re halfway there Theodore Roosevelt Variables and Types in Java Declaring Variables in Java Variabled are used to store and manipulate data in Java There are three types of variables local instance and class or static Local Variables Local variables are declared inside a method and are only accessible within that method Here s an example public class Main public static void main String args int counter 0 declaring and initializing a local variable counter incrementing the counter System out println counter printing the value of counter As you can see we declare a local variable counter and initialize it to zero We then increment the counter and print its value Instance Variables public class Circle Instance variables are declared outside any method but inside a class and they are accessible from within any method in that class Here s an example private double radius declaring an instance variable public Circle double radius constructor this radius radius initializing the instance variable public double getArea method that calculates the area of the circle return Math PI radius radius public class Main public static void main String args Circle circle new Circle 5 creating a new circle with a radius of 5 System out println circle getArea printing the area of the circle In this example we declare an instance variable radius in the Circle class We then initialize the variable in the constructor and use it to calculate the area of the circle Class or Static Variables Class variables also called static variables are declared using the static keyword and are shared by all instances of the class Here s an example public class Counter private static int count 0 declaring a class variable public Counter constructor count incrementing the class variable public static int getCount method that returns the class variable return count public class Main public static void main String args Counter c1 new Counter creating a new counter Counter c2 new Counter creating another counter System out println Counter getCount printing the count 2 In this example we declare a class variable count in the Counter class We then increment the variable in the constructor and provide a static method getCount to access the variable Naming Conventions Java has strict naming conventions for variables Here are some tips Variable names should be descriptive and written in camelCase with the first letter lowercase and the first letter of each subsequent word capitalized For example firstName lastName socialSecurityNumber Constant names should be written in all uppercase with words separated by underscores For example MAX VALUE MIN VALUE PI Do not use any Java keywords or reserved words as variable names Data Types Java supports several data types including Numeric types byte short int long float double and various wrapper classes e g Byte Short Integer Long Float Double Character type char Boolean type boolean String type String Introduction In this chapter we will cover the basic data types in Java including Numbers int long float double and their respective wrappers Characters char Booleans boolean Numbers Integers Java supports several types of numbers including integer and floating point numbers Here are the most commonly used ones int A 32 bit signed integer which can store values between 2 31 and long A 64 bit signed integer which can store values between 2 63 and 2 31 1 about 2 billion 2 63 1 about 9 quintillion Here s an example of how to use int and long int myInt 42 long myLong 42 000 000 000L Note the L suffix to indicate a long value Java also provides the following integer wrapper classes which can be useful when working with libraries or APIs that expect objects instead of primitive types Integer for int Long for long Floating point numbers float A 32 bit floating point number which can store values between approximately 1 4e 45 and 3 4e 38 double A 64 bit floating point number which can store values between approximately 4 9e 324 and 1 7e 308 Here s an example of how to use float and double float myFloat 3 141592653589793f Note the f suffix to indicate a float value double myDouble 3 141592653589793 Java also provides the following floating point wrapper classes which can be useful when working with libraries or APIs that expect objects instead of primitive types Float for float Double for double Important note Floating point numbers can be imprecise due to their binary representation Therefore it s generally recommended to use double for higher precision and avoid comparing floating point numbers for equality Characters char myChar A Java represents individual characters using the char data type which is a 16 bit Unicode character Here s an example of how to use char You can also use Unicode escape sequences to represent special characters such as char mySpecialChar u00A9 Copyright symbol Java represents boolean