Programming Fundamentals/Variable Examples Java

Overview

The following examples demonstrate data types, arithmetic operations, and input in Java.

Data Types

 // This program demonstrates variables, literal constants, and data types.
 
 public class Main {
     public static void main(String[] args) {
         int i;
         double d;
         String s;
         boolean b;
         
         i = 1234567890;
         d = 1.23456789012345;
         s = "string";
         b = true;
 
         System.out.println("Integer i = " + i);
         System.out.println("Double d = " + d);
         System.out.println("String s = " + s);
         System.out.println("Boolean b = " + b);
     }
 }

Output

Integer i = 1234567890
Double d = 1.23456789012345
String s = string
Boolean b = true

Discussion

Each code element represents:

// begins a comment
public class DataTypes begins the Data Types program
{ begins a block of code
public static void main(String[] args) begins the main function
int i defines an integer variable named i
; ends each line of Java code
double d defines a double floating-point variable named d
string s defines a string variable named s
boolean b defines a Boolean variable named b
i = , d = , s =, b = assign literal values to the corresponding variables
System.out.println calls the standard output print line function
} ends a block of code

Arithmetic

 // This program demonstrates arithmetic operations.
 
 public class Main {
     public static void main(String[] args) {
         int a;
         int b;
         
         a = 3;
         b = 2;
 
         System.out.println("a = " + a);
         System.out.println("b = " + b);
         System.out.println("a + b = " + (a + b));
         System.out.println("a - b = " + (a - b));
         System.out.println("a * b = " + a * b);
         System.out.println("a / b = " + a / b);
         System.out.println("a % b = " + (a % b));
     }
 }

Output

a = 3
b = 2
a + b = 5
a - b = 1
a * b = 6
a / b = 1
a % b = 1

Discussion

Each new code element represents:

+, -, *, /, and % represent addition, subtraction, multiplication, division, and modulus, respectively.

Temperature

 // This program converts an input Fahrenheit temperature to Celsius.
 
 import java.util.*;
 
 public class Main {
     private static Scanner input = new Scanner(System.in);
 
     public static void main(String[] args) {
         double fahrenheit;
         double celsius;
         
         System.out.println("Enter Fahrenheit temperature:");
         fahrenheit = input.nextDouble();
 
         celsius = (fahrenheit - 32) * 5 / 9;
         
         System.out.println(Double.toString(fahrenheit) + "° Fahrenheit is " + celsius + "° Celsius");
     }
 }

Output

Enter Fahrenheit temperature:
 100
100° Fahrenheit is 37.7777777777778° Celsius

Discussion

Each new code element represents:

private static Scanner input ... defines an object to read from standard input
input.nextDouble() reads input as a double floating-point value

References

Wikiversity: Computer Programming

Programming Fundamentals