Types Of Data In Java: All You Need To Know
In Java, data types identify what kind of data can be held within a variable as well as what possible operations can be carried out with that variable. This guarantees that type errors and other errors are eliminated at compile time. Having a solid understanding of Java’s data types is crucial in coming up with robust and efficient code.
Java data types can be categorically divided into Two classes being the Primitive Data Types and the Non Primitive (Reference) Data Types.
Data types in Java
Table of Contents
- Primitive Data Types
It has been noted that they are provided for by the Java language and thus is the foundation upon which data resources the are the eight primitive data types in Java with each being suited specifically for certain types of data and memory use.
Numeric Data Types
It is fairly self-evident that numeric data types are responsible for holding numbers. they can be further subdivided even more in to two separate groups which are: integral and floating point.
Integral Types
byte
Size: 8 bit
Range: -128 to 127
Default Value: 0
Use Case: Used for mass storage of large arrays or when working with data streams from a file or a network so as to save memory.
Let’s look into the four primary numeric data types available in Java. In the below table, the size, range of values allowed, and the default value are stipulated for all the types:
Primitive Data Type
1.short
Size: 16 bits
Range: -32,768 to 32,767
Default Value: 0
Use Case: Can be used for memory optimization when range of values required to be stored lies within its limit.
2.int
Size: 32 bits
Range: -2^31 to 2^31-1
Default Value: 0
Use Case: Most frequently used integral data type for arithmetic operations in general computations.
3.long
Size: 64 bits
Range: -2^63 to 2^63-1
Default Value: 0L
Use Case: When a bigger range than int is required such as in case of big calculations or for storing dates and time where in seconds are required.
Floating Point Types
The floating point types are used for preserving decimal numbers.
1.float
Size: 32 bits
Range: Approximately ±3.40282347E+38F
Default Value: 0.0f
Use Case: Used when storing data which will required a fraction of maximum up to 6 – 7 digits after decimal point.
2.double
Size: 64 bits
Range: Approximately ±1.79769313486231570E+308
Default Value: 0.0d
Use Case: For calculations where high degree of accuracy is necessary e.g. scientific calculations with precision of up to 15 – 16 digits after decimal point.
Non- Numeric Data types
These types can be used for such classes of data which includes boolean values and characters.
1.char
Size: 16 bits
Range: 0 to 65,535 (unsigned)
Default Value: ‘\u0000’ (null character)
Use Case: A single character or Unicode symbol is stored using this case.
boolean
Size: A number that is not exactly specified (internally, it has an integer representation that is usually one bit).
Values: True or false.
Default Value: false.
Use Case: Used for conditions, flags, and logical operators.
- Non-Primitive (Reference) Data Types
Non primitive data types are complex types that are used to store references to objects. In contrast to the primitive data types, they are not built-in and consist of classes, interfaces, arrays and enums.
2.1. Classes
Classes are blueprints of the objects. A Java class can set up attributes (fields) and give the object functions (methods) to perform specific actions.
Example:
class Car {
String model;
int year;
}
2.2. Arrays
An array is a set of same type of variables. Arrays may be of one-dimension or multidimensional.
Declaration and Initialization:
int[] numbers = new int[5]; // An array of integers containing 5 elements
String[] names = new String[] {“Alice”, “Bob”, “Charlie”};
Accessing Elements:
System.out.println(numbers[0]); // First element access
2.3. Interfaces
Interfaces are abstract data types that define a contract in terms of the behavior that the implementing classes would need to provide. Data cannot be directly contained in interfaces; instead, methods are defined which the class must implement.
Example:
interface Animal {
void eat();
void sleep();
}
2.4. Enums
Enums are a group of constants which are constant in nature. They are often used to represent concept like Months, Days, Weeks etc.
Example:
enum Day {
MON, TUESDAY, WED, THU, FRIDAY, SAT, SUNDAY
}
- Type Conversion and Casting
In Java there are instances that permit the change of one data type into another.
3.1. Implicit Casting (Widening Conversion)
Java automatically promotes from a small data type to a big one.
Example:
int a=10;
long b=a; //Implicit casting
3.2. Explicit Casting (Narrowing Conversion)
You need to convert larger data type into smaller data type but there is risk of losing data.
Example:
double a=10.5;
int b = (int)a; //explicit casting
- Wrapper Classes
In Java, there are Wrapper Classes for each of the primitive types which extends the functionality associated with that type. These classes belong to java.lang package.
int num=10;
Integer numWrap = new Integer(num);// Boxing
int numUnwrap = numWrap.intValue();// Unboxing
- Memory Allocation and Performance
5.1. Memory Allocation
Primitive Data Types: these are usually very easy to access and therefore are stored directly in the stack.
Reference Data Types: these ones are stored within the heap and a reference to them is kept in the stack.
5.2. Performance
Primitive compose of minimal necessary storage while being faster to execute Non-primitive pose as an easier approach of handling types but at the expense of more overhead.
- Special Data Types in Java6.1. Null Type
The meaning of nil implies the absence of an object reference within the reference variable, and it excludes the use of primitive types.
6.2. String Type
A String is a group of characters. String is one of the classes among others that Java provides for text manipulation.
- Key Points to Remember
Never pick a single data type that would work in all situations, as it might work for performance optimization while doing a poor job in memory utilization.
As a guideline, use float and double but be careful when it comes to making comparisons as errors in precision may occur.
Another example is that an array is of constant length and is set once only; for a changing length use collections such as ArrayList.
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Conclusion
Recognize that data types are the building blocks of the Java type system and that when dealing with programming, the types of primitive and non-primitive revolve around a well-thought-out and sophisticated piece of code. Although non-primitive expects more work, it becomes ideal for large scale and complex systems. Understanding data types is an important step towards being excellent in Java programming interoperability.