Understanding Data Types in Java: A Comprehensive Guide

Java is a powerful and versatile programming language that is widely used in various applications, from web development to mobile apps. Understanding its data types is essential for any Java programmer.

Java is known for being a statically typed and strongly typed language. This means that every piece of data used in a Java program has a specific type, such as integer, character, or floating-point number, and these types are defined as part of the language itself.

In Java, data types are essential because they define the size and value range of the data that can be stored in a variable. This helps ensure that the data is handled correctly and efficiently, avoiding potential errors and enhancing performance.

It's crucial to use the correct data types in your Java programs to prevent runtime errors and improve code readability and maintainability.

Java's data types are divided into two main categories:

• Primitive Data Types
• Non-Primitive Data Types

Primitive data types are the building blocks of data manipulation in Java, encompassing basic types such as int, char, and boolean. On the other hand, non-primitive data types, also known as reference types, include classes, arrays, and interfaces, which are more complex structures that can store multiple values or represent objects.

In this guide, we will explore both categories of data types, providing examples and explanations to help you understand how to use them effectively in your Java programs.

Table of Contents

Primitive Data Types in Java

Primitive data types in Java are the most basic types of data that are built into the language. They serve as the foundation for data manipulation and are not objects.

There are 8 primitive data types in Java:

Type	Description	Default	Size	Example Literals	Range of Values
boolean	True or false	false	8 bits	true, false	true, false
byte	Twos-complement integer	0	8 bits	(none)	-128 to 127
char	Unicode character	\u0000	16 bits	'a', '\u0041', '\101', '\\', '\', '\n', 'β'	0 to 65,535
short	Twos-complement integer	0	16 bits	(none)	-32,768 to 32,767
int	Twos-complement integer	0	32 bits	-2, -1, 0, 1, 2	-2,147,483,648 to 2,147,483,647
long	Twos-complement integer	0	64 bits	-2L, -1L, 0L, 1L, 2L	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
float	IEEE 754 floating point	0.0	32 bits	1.23e100f, -1.23e-100f, .3f, 3.14F	Up to 7 decimal digits
double	IEEE 754 floating point	0.0	64 bits	1.23456e300d, -123456e-300d, 1e1d	Up to 16 decimal digits

1. Boolean Data Type

The Boolean data type represents a logical value that can be either true or false. While it conceptually represents a single bit of information, the size of the Boolean data type is virtual machine-dependent and is typically one byte (eight bits) in practice.

boolean booleanVar;

Size: Virtual machine dependent

2. Byte Data Type

The byte data type is an 8-bit signed two’s complement integer. The byte data type is useful for saving memory in large arrays.

byte byteVar;

Size: 1 byte (8 bits)

3. Short Data Type

The short data type is a 16-bit signed two’s complement integer. Similar to byte, use a short to save memory in large arrays, in situations where the memory savings actually matters.

short shortVar;

Size: 2 bytes (16 bits)

4. Integer Data Type

It is a 32-bit signed two’s complement integer.

int intVar;

Size: 4 bytes (32 bits)

In Java SE 8 and later, we can use the int data type to represent an unsigned 32-bit integer, which has a value in the range [0, 2³²-1]. Use the Integer class to use the int data type as an unsigned integer.

5. Long Data Type

The range of a long is quite large. The long data type is a 64-bit two’s complement integer and is useful for those occasions where an int type is not large enough to hold the desired value.

long longVar;

Size: 8 bytes (64 bits)

In Java SE 8 and later, you can use the long data type to represent an unsigned 64-bit long, which has a minimum value of 0 and a maximum value of 2⁶⁴-1. The Long class also contains methods like comparing Unsigned, divide Unsigned, etc. to support arithmetic operations for unsigned long.

6. Float Data Type

The float data type is a single-precision 32-bit IEEE 754 floating-point. Use a float (instead of double) if you need to save memory in large arrays of floating-point numbers.

float floatVar;

Size: 4 bytes (32 bits)

7. Double Data Type

The double data type is a double-precision 64-bit IEEE 754 floating-point. For decimal values, this data type is generally the default choice.

double doubleVar;

Size: 8 bytes (64 bits)

Note: Both float and double data types were designed especially for scientific calculations, where approximation errors are acceptable. If accuracy is the most prior concern then, it is recommended not to use these data types and use BigDecimal class instead.

8. Char Data Type

The char data type is a single 16-bit Unicode character.

char charVar;

Size: 2 bytes (16 bits)

Other languages like C/C++ use only ASCII characters, and to represent all ASCII characters 8 bits is enough. But Java uses the Unicode system not the ASCII code system and to represent the Unicode system 8 bits is not enough to represent all characters so Java uses 2 bytes for characters. Unicode defines a fully international character set that can represent most of the world’s written languages. It is a unification of dozens of character sets, such as Latin, Learn, Cyrillic, Katakana, Arabic, and many more.

Related Posts

Non-Primitive Data Types in Java

Non-primitive data types in Java, also known as reference data types, are not predefined by the language and can be used to store more complex data structures.

The main non-primitive data types in Java are Strings, Classes, Objects, Interfaces, and Arrays.

1. Strings

Strings are defined as an array of characters. The difference between a character array and a string in Java is that a string is designed to hold a sequence of characters in a single variable, whereas a character array is a collection of separate char-type entities. Unlike C/C++, Java strings are not terminated with a null character.

Syntax: Declaring a string

String s = "LearnTricking";

String s1 = new String("LearnTricking");

2. Class

A class is a user-defined blueprint or prototype from which objects are created. It represents the set of properties or methods that are common to all objects of one type. In general, class declarations can include these components, in order:

• Modifiers: A class can be public or have default access. Refer to access specifiers for classes or interfaces in Java.
• Class name: The name should begin with an initial letter (capitalized by convention).
• Superclass (if any): The name of the class’s parent (superclass), if any, preceded by the keyword extends. A class can only extend (subclass) one parent.
• Interfaces (if any): A comma-separated list of interfaces implemented by the class, if any, preceded by the keyword implements. A class can implement more than one interface.
• Body: The class body is surrounded by braces, { }.

3. Object

An object is a basic unit of Object-Oriented Programming and represents real-life entities. A typical Java program creates many objects, which interact by invoking methods. An object consists of:

• State: It is represented by the attributes of an object. It also reflects the properties of an object.
• Behavior: It is represented by the methods of an object. It also reflects the response of an object to other objects.
• Identity: It gives a unique name to an object and enables one object to interact with other objects.

4. Interface

Like a class, an interface can have methods and variables, but the methods declared in an interface are by default abstract (only method signature, no body). Interfaces specify what a class must do and not how. It is the blueprint of the class.

• An interface is about capabilities like a Player may be an interface and any class implementing Player must be able to (or must implement) move(). So it specifies a set of methods that the class has to implement.
• If a class implements an interface and does not provide method bodies for all functions specified in the interface, then the class must be declared abstract.
• A Java library example is the Comparator Interface. If a class implements this interface, then it can be used to sort a collection.

5. Array

An Array is a group of like-typed variables that are referred to by a common name. Arrays in Java work differently than they do in C/C++. The following are some important points about Java arrays:

• In Java, all arrays are dynamically allocated.
• Since arrays are objects in Java, we can find their length using the member length. This is different from C/C++ where we find length using size.
• A Java array variable can also be declared like other variables with [] after the data type.
• The variables in the array are ordered and each has an index beginning with 0.
• Java arrays can also be used as static fields, local variables, or method parameters.
• The size of an array must be specified by an int value and not long or short.
• The direct superclass of an array type is Object.
• Every array type implements the interfaces Cloneable and java.io.Serializable.

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FQAs

What are Data Types in Java?

Data types in Java vary in size and the values they can store, tailored for different needs and situations to handle all possible scenarios.

What are the 8 primitive data types in Java?

The 8 main primitive data types in Java are boolean, byte, char, short, int, long, float, and double.

What is a primitive data type in Java?

Primitive data types are basic types in Java that store single values and do not provide any special capabilities. Examples include int, boolean, and char.

Why does char use 2 bytes in Java and what is \u0000?

Char uses 2 bytes in Java because it uses the Unicode system instead of the ASCII system. \u0000 is the lowest range of the Unicode system.