Tag Archives: type

Data types in Java

A data type classifies various types of data eg. String, integer, float, boolean, the types of accepted values for that data type, operations that can be performed on the data type, the meaning of the data, and the way that data of that type can be stored.

The table below shows the most commonly used data types used in the Java programming language.

Type Description Example
int The integer (int) data type stores positive or negative whole number values. 20
float The float data type stores floating point numbers (numbers with decimal places) eg. 43.65 . Often, you will need to end a float value with an ‘f’ character eg. 43.65f 43.65f
char The char data type stores a single character such as a letter, number, space or special character (eg. a, 1, !).  A char value is always surrounded by single quotes eg. ‘a’. ‘a’
String The String data type stores letters, numbers and other characters in the form of words or sentences. A string value is always surrounded by double quotes eg. “Hello World”. “Hello world”
boolean The boolean data type stores true or false values only eg. true true

The table below shows some of the other data types used in the Java programming language.

Type Description Example
byte The byte data type stores integer numbers ranging from -128 to +127 118
short The short data type is used for integer numbers ranging from -32,768 to +32,767 -28,471
long The long data type is used for integer values exceeding 2.14 billion ‘a’
double The double data type is used for extremely long floating point numbers 1.7976931348623157 × 10^308

Sample code

The sample Java code below shows how some of the different data types can be stored in variables. Later on, we will look at how to actually work with the values of different data types (eg. math calculations with integers and floats, and decision making with booleans).

The code includes comments explaining each data type.

package myjavaproject;

public class DataTypes {
    public static void main (String[] args){
        String message = "Hello"; // variable of String data type
        char letter = 'a'; // variable of char data type
        int number = 20; // variabe of int (integer) data type
        float decimal = 43.65f; // variable of float (floating point) data type
        boolean result = true; // variable of Boolean data type
        
        // now let's output the values of the different variables
        System.out.println("Message is " + message);
        System.out.println("Letter is " + letter);
        System.out.println("Age is " + number);
        System.out.println("Score is " + decimal);
        System.out.println("The answer is " + result);
    }
}

Integers and floats in C#

In the previous tutorial we looked at how to create variables and work with the string data type in C#. In this tutorial we will look at how to work with the integer and float data types in C# and also how to convert strings to integers or floats using the int.Parse() and float.Parse() methods. You will also learn how to manipulate numbers using arithmetic operators.

Watch the video below or scroll down to see the sample code.

Sample C# code

using System;

namespace MyCSharpApp
{
  class MainClass

  {
    public static void Main (string[] args)
    {
      Console.WriteLine ("Enter two numbers...");
      float num1 = float.Parse(Console.ReadLine ());
      float num2 = float.Parse(Console.ReadLine ());
      Console.WriteLine (num1 + num2);
    }
  }
}

Arithmetic operators

Arithmetic operators are used for performing standard math operations on variables and are usually only used number variables (although they can be used for other things too).

Operator Name / description
+ Addition – this operator is used to add two numbers together. It can also be used to concatenate (join) two strings together.
Subtraction – this operator is used to subtract one number from another.
* Multiplication – this operator is used to multiply two numbers together.
/ Division – this operator is used to divide one number by another.
% Modulus – this operator is used to divide one number by another but instead of returning the result, it returns the remainder of the division. Eg. 5%2 would return a result of 1.

Brackets can also be used for more complex math operations eg. 5 + (10 * (6 / 3) / 2);

The assignment operators follow standard mathematic order of operations. That means that the math works from left to right. Parenthesis are done first, multiplication and division comes second, and then addition and subtraction come third.

Assignment operators

Assignment operators are used to assign a value to a variable. The most frequently used assignment operator is the equals (=) sign. There are other operators as well that are used to combine multiple operations into one. The syntax of a standard variable assignment looks like this:

<variable name> <assignment operator> <value>;

For example: x = 5;

The table below shows the different assignment operators available in C#.

Operator Description
= The equals sign is used to assign the value on the right side of the equals sign to the variable on the left side of the equals sign.
+= , -= , *= and /= These assignment operators are also used to perform arithmetic operations and assign the result to the variable eg. x *= 5 is the same as saying x = x * 5.
++ and — These assignment operators are called increment and decrement operators and are used to increase or decrease the value of a variable by 5. For example, x++ is the same as saying x = x + 1.

Next tutorial: Conditional programming in C#

Styling lists

In one of the earlier tutorials we looked at how to create lists in a HTML web page. In this tutorial we will look at how to style both ordered and unordered lists using CSS code. We can style lists by changing circles to other shapes such as squares or arrows, or we can make lists ordered by letter instead of number, as an example.

Take a look at the example below where the order list has been styled to use letters instead of numbers, and the unordered list has been styled to use squares instead of circles.

Screen Shot 2017-04-14 at 4.41.21 pm

By adding the code display:inline; for the li element in your CSS code you can also show list items horizontally instead of vertically, as seen below.

Screen Shot 2017-04-14 at 4.43.34 pm

Watch the video below and then scroll down to see the sample code.

Here is the sample HTML code:

<!DOCTYPE html>
<html>
<head>
 <title>Styling lists</title>
 <meta charset="utf-8"/>
 <link rel="stylesheet" href="resources/stylesheet12.css" type="text/css"/>
</head>
<body>
 <h2>Cities</h2>
 <ol class="cities">
 <li>Sydney</li>
 <li>Melbourne</li>
 <li>Brisbane</li>
 <li>Perth</li>
 </ol>

 <h2>Countries</h2>
 <ul class="countries">
 <li>Australia</li>
 <li>France</li>
 <li>Canada</li>
 <li>New Zealand</li>
 </ul>
</body>
</html>

And here is the sample CSS code:

ol{
 list-style-type:lower-alpha;
 color:blue;
}

ul{
 list-style-type:square;
 color:green;
}

You can also add the following to your CSS code if you want list items to display horizontally:

li{
display: inline;
}