Core Lesson 2 : Data Types in Java

March 01, 2021 Anil Sable

So, In this chapter, we would be learning about the various data types available in java and how to declare them, and how to use them in our java program. It is mostly similar to the C and C++ programming languages. Java is a strongly typed language. Every variable has a type, every expression has a type and java always ensures before store data in the variable, do they match the type of variable we have declared.

How to Declare a variable

Syntax :

datatype var1 [= init_val], var2 = [init_val], . . . ;

The above syntax shows how to declare a variable in java. You can declare one variable in one line and at the end, you have to specify a semicolon. you can declare more than one variable on a single line separated by a comma. you can also initialize their values while declaring them. Let's have a look at the below program which shows different ways by which we can declare and initialize variables.

public class DataTypeDemo {
    public static void main(String args[]) {

        int singleLineVariable;
        int anotherSingleLineVariable=10;
        int multipleVariableOnSameLine1, multipleVariableOnSameLine2;
        int multipleVariableOnSameLineWithInitValue1= 10, multipleVariableOnSameLineWithInitValue2= 20;
        int dynamicallyInitializedVariable = anotherSingleLineVariable * 20;

    }
}

Primitive Types

Primitive type refers to a simple type. they represent a single value at a time. unlike complex objects like structure or class. Although java is a completely object-oriented programming language; the exception is for the primitive type. We do have Wrapper classes for each primitive type we will check that out also going ahead in this blog. the reason for keeping primitive types in java is that speeding up the performance of the program.

Let's have a look at the different simple types available in java

Numeric Data Type

Integer numbers

long (range : –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)
int (range : –2,147,483,648 to 2,147,483,647)
short (range :–32,768 to 32,767)
byte (range : –128 to 127)

Integers are nothing but the Whole numbers in mathematical terms. They represent all signed positive to negative numbers as per their data type. Java does not support unsigned integer types as many other programmings do. Let's have a look at the below example for the Integer declaration

class DataTypeDemo {
    public static void main(String args[]) {
        byte var1 = 10; // Declaring byte variable with initial value of 10
        short var2 = 20; // Declaring short variable with initial value of 20
        int var3 = 40; // Declaring int variable with initial value of 40
        long var4 = 80; // Declaring long variable with initial value of 80
    }
}

Java Also supports Octal, Hexa Decimal, and Binary numbers. Let's have a look at the below program to know how we can declare the integer in the different number system

class DifferentNumberSystems {
    public static void main(String args[]) {

        // octalNumber value can be declare by leading 0 before number
        // blow is the declaration of 10 octal number which is 8
        int octalNumber = 010;
        System.out.println(octalNumber);

        // hexaDecimal value can be declare by leading 0x before the number
        // below is the declaration of 0x1A hexa number which is 26
        int hexaDecimalNumber = 0x1A;
        System.out.println(hexaDecimalNumber);

        // binaryNumber value can be declare by leading 0b before the number
        // below we have declare binary version of 172
        int binaryNumber = 0b10101100;
        System.out.println(binaryNumber);

    }
}

Floating Point numbers

double (64 bit)
float (32 bit)

Floating-point numbers represent decimal values with a fractional component. They can be expressed in either standard or scientific notation. Standard notation consists of a whole number component followed by a decimal point followed by a fractional component. For example, 2.0, 3.14159, and 0.6667 represent valid standard-notation floating-point numbers. Scientific notation uses a standard-notation, floating-point number plus a suffix that specifies a power of 10 by which the number is to be multiplied. The exponent is indicated by an E or e followed by a decimal number, which can be positive or negative. Examples include 6.022E23, 314159E–05, and 2e+100.

Floating-point literals in Java default to double precision. To specify a float literal, you must append an F or f to the constant. You can also explicitly specify a double literal by appending a D or d. Doing so is, of course, redundant. The default double type consumes 64 bits of storage, while the smaller float type requires only 32 bits. Let's have a look at below example

public class DataTypeDemo {
    public static void main(String args[]) {

        // declaring float variable 
        // Notice f at the end of the number
        float var1 = 10.5f;
        
        // declare double variable
        double var2 = 3.14;
        
    }
}

Using Separators in the numeric type

You must have seen in mathematical books when it comes to defining large number; we use a comma as a separator value
This allows the reader to quickly grasp the value of the number by grouping them
java allows us to specify separator while you declare the number type values
Separator allowed here is underscores character (_)

Let's have a look at the below java example to define a very large number that is easily readable

// Internation format
// one hundred and twenty three million four hundred and fifty six thousand seven hundred and eighty nine
int veryLargeNumber = 123_456_789;

// Indian format
// twelve crore thirty four lakh fifty six thousand and seven hundred and eighty nine
int anotherVeryLargeNumber = 12_34_56_789;

// Value of pi with separator 
double fractionalNumber = 3.141_592_653;

Non-Numeric Data Type

Characters

In Java, the data type used to store characters is char
char in Java is not the same as char in C or C++
In C/C++, char is 8 bits wide uses ASCII charset. Instead, Java uses Unicode charset.
Unicode defines a fully international character set that can represent all of the characters found in all human languages.
Unicode required 16 bits. Thus, in Java char is a 16-bit type.

Let's have a look at the below program that can give you an idea about using characters in java

public class DataTypeDemo {
    public static void main(String args[]) {
        char firstCharVariable = 'A';
        char nextCharVariable = 'B';
        char smallCaseLetterVariable = 'h';
    }
}

Booleans

Java has a primitive type, called boolean, for logical values
It can have only one of two possible values, true or false
This is the type returned by all relational operators, as in the case of a < b
Boolean is mostly used in control execution commands we would be going to learn ahead
The values of true and false do not convert into any numerical representation
The true literal in Java does not equal 1, nor does the false literal equal 0

Let's have a look at the below example which will demonstrate common usage of boolean

public class DataTypeDemo {
    public static void main(String args[]) {

        boolean hasVisa = false;
        boolean hasJob = true;
        boolean isEligibleForVoting = true;

        if(isEligibleForVoting) {
            System.out.println("Person is eligible for Voting");
        }
        else {
            System.out.println("Person is Not eligible for Voting");
        }
    }
}

String Data type

String is a Complex data type in java. It is not like the primitive data type. String is a Class in java. String object has a whole bunch of methods available to it. If you have seen the above primitive data type they don't have a method on them which means they are just placeholders to store data on them that can be used for calculation directly. you can not do much on the primitive data type. But String in java is not primitive, you can do a lot of operations on string objects like converting them to lower case, uppercase, concatenate, substring, and so on. We have a separate chapter on String going ahead in this blog.

Let's have a look at the below example of using String data type

public class DataTypeDemo {
    public static void main(String args[]) {

        String str1 = "Hello this is java program";
        String str2 = "This is another line";

        String str3 = str1.toUpperCase();

        System.out.println(str1);
        System.out.println(str2);
        System.out.println(str3);
    }
}

Important Points to Remember from these lessons

We can declare more than 1 variable on the same line of the same data type
we can initialize more than 1 variable on the same line of the same data type
Java is a strictly typed language. so you cannot assign float to int or float to char
We can also initialize number in octal, binary, or hexadecimal format
String is not primitive data type. It is a Complex data type in java
The primitive variable doesn't have any member function on them
Since String is not primitive it has a member function defined inside it

So that All for this Lesson, Let me know if you did not understand anything on this lesson in below comment section, I will try to revert your or I will improve this lesson in this blog.

Till then Good Bye, Happy Coding !!!

Java 4 Ninja

Monday, March 1, 2021