Java Data types

If you’ve ever found yourself scratching your head over terms like integers, strings, or booleans, fear not – we’re here to demystify it all and make it as clear as a sunny day.

Before we dive into the specifics, let’s start with the basics. What exactly are data types? Well, think of them as categories or classifications that tell Java how to interpret and manipulate data. They define the type of values that can be stored in a variable and the operations that can be performed on those values.

NOTE

Java is what we call “statically typed.” What does that mean? Well, it means that every variable and expression in Java has a type that’s known at compile time. In simpler terms, when you’re coding in Java, you need to declare the type of each variable before you can use it. This helps the compiler catch errors early on and ensures that your code is solid from the get-go.

Types of Data Types:

In Java, data types can be broadly categorized into two main groups: primitive data types and reference data types. Let’s delve into each category and unravel its mysteries:

Primitive Data Types:​

Primitive data types represent the most basic types of data that Java can handle. They are predefined by the language and are not objects. Primitive data types include:

• Integer Types:

Data Type	Size (in bits)	Minimum Value	Maximum Value	Example
byte	8	-128	127	byte num = 100;
short	16	-32,768	32,767	short num = 1000;
int	32	-2^31	2^31 – 1	int num = 100000;
long	64	-2^63	2^63 – 1	long num = 1000000000L;

• Floating-Point Types:

Data Type	Size (in bits)	Minimum Value	Maximum Value	Example
float	32	Approximately 1.4E-45	Approximately 3.4E+38	float num = 3.14f;
double	64	Approximately 4.9E-324	Approximately 1.8E+308	double num = 3.14;

• Character Type:

Data Type	Size (in bits)	Minimum Value	Maximum Value	Example
char	16	‘\u0000’	‘\uffff’	char letter = ‘A’;

• Boolean Type:

Data Type	Size (in bits)	Minimum Value	Maximum Value	Example
boolean	Not Applicable	false	true	boolean isTrue = true;

Reference Data Types:​

Reference data types, also known as object data types, refer to objects created using classes. They are stored in the heap memory and can hold a reference (address) to the actual data. Common examples of reference data types include:

• String:String name = "John Doe";
• Array:int[] numbers = {1, 2, 3, 4, 5};

TIP

In Java, when we talk about reference data types, it’s not just about built-in stuff like strings and arrays. Your very own custom-made classes also fall into this category! So, whether you’re using a class you built yourself or one that comes pre-packaged with Java, if it’s not a primitive type, it’s a reference type.

Example

1. Integer Types:

java

byte numByte = 100;      // 8-bit signed integer
    short numShort = 1000;   // 16-bit signed integer
    int numInt = 100000;     // 32-bit signed integer
    long numLong = 1000000000L; // 64-bit signed integer (note the 'L' suffix)

2. Floating-Point Types:

java

float numFloat = 3.14f;  // 32-bit floating-point number (note the 'f' suffix)
    double numDouble = 3.14; // 64-bit floating-point number

3. Character Type:

java

char letter = 'A';       // 16-bit Unicode character

4. Boolean Type:

java

boolean isTrue = true;   // Boolean value: true or false`

5. String (Reference Type):

java

String name = "John Doe"; // Reference to a string object`

6. Array (Reference Type):

java

int[] numbers = {1, 2, 3, 4, 5}; // Array of integers`

java

public class DataTypesExample {
    // Primitive data types
    byte numByte = 100;         // 8-bit signed integer
    short numShort = 1000;      // 16-bit signed integer
    int numInt = 100000;        // 32-bit signed integer
    long numLong = 1000000000L; // 64-bit signed integer
    float numFloat = 3.14f;     // 32-bit floating-point number
    double numDouble = 3.14;    // 64-bit floating-point number
    char letter = 'A';          // 16-bit Unicode character
    boolean isTrue = true;      // Boolean value: true or false
    
    // Reference data types
    String name = "John Doe";       // Reference to a string object
    int[] numbers = {1, 2, 3, 4, 5}; // Array of integers
    
}