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Engineering LibreTexts

2.19: Java Examples

  • Page ID
    10615
  • 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