Java custom data type class

Java User-defined Data Types

Java User-defined data types are the customized data types created by the developers by exploiting the special features offered by the Java language. This customized data type combines data types of a group of data elements with homogenous or assorted data types. It utilizes the object-oriented functionalities of Java and allows creation of any kind of data types as per the need.

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These data types have versatile characteristics and behavior and it provides greater flexibility to developers in improving their productivity and maintainability of the programs. Let’s go through features of these special data types in this article.

Data types of all the variables should be declared well ahead of its compilation and it should be one from the standard type that Java offers. The variables cannot hold any other data type than what was declared. But the user-defined data type provides the flexibility to define the data type at a group level.

User-defined Data Types in Java

Two major User defined data types are:

1. Class

Java a true object-oriented language is full of Classes that encapsulate everything from data elements that acts as instance variables and functions to process the data. It also provides templates to create Objects that are instances of Class that contain a method for performing the defined functions and interact with other parts of the program.

A class typically contains

Invoking variables with data types

How Objects are created?

Objects are created or instantiated from the class and used as individual instance of the class. Instance variables are created for each of the objects to interact with other components of the program and there could be as many objects created and each object will have

• Clear identity with a unique name
• Different set of instance variables to reflect its state.
• All the functionalities that define its behavior

Each class is a user-defined data type with the combined effect of all the data types of its data elements and each object is a variable data.

Example #1: Class Definition

// Sample program to define Class, Object and Method class ValueStore //Class definition with default access < int Rate; // Variables with standard data types int Qty; void AssignData(int A, int B) // method definition < Rate = A; // Assigning the values Qty = B; >int ComputeValue() // Another method to compute value < int value; // variable definition value = Rate * Qty; return(value); // Returning the value >>

Class with name ValueStore with default access is defined. It has two instance variables Rate, QTY used in the method interactions. Two methods AssignData, ComputeValue with respective function codes are created inside the class.

public class OrderValueCompute // Public class < public static void main(String[] args) // Execution starts here < int value1; // variable definition int value2; ValueStore VS1; // Object VS1 definition VS1 = new ValueStore(); // Object VS1 instantiated ValueStore VS2; // Object VS2 definition VS2 = new ValueStore(); // Object VS2 instantiated VS1.AssignData (200,10); // Assigndata method in Object VS1 invoked //with values value1 = VS1.ComputeValue(); // Computedata method in object VS1 // invoked VS2.AssignData (500,20); // Assigndata method in Object VS2 // invoked with values value2 = VS2.ComputeValue(); // Computedata method in object VS2 //invoked System.out.println("Order value 1 " +value1); // Output 1 displayed System.out.println("Order Value 2 " +value2); // Output 2 displayed >>

In the execution class, the objects in the other class are defined, instantiated. Methods are invoked. Results obtained and displayed. Class is a user-defined data type and each object is a variable in it.

2. Interface

Interface is similar to Class in architecture. It has data variables and methods. It broadly suggests what the classes calling it should do but it does not suggest how it should be carried out.

The method in an interface differs from a normal method in a class by

• It is not full-fledged
• It is only an abstract and it has the only a definition and the body is empty.
• It will not perform any functionalities as such

Interfaces cannot instantiate any objects like class. But it facilitates abstraction, Multiple inheritances, and loose coupling of classes.

Class extends to another super class by a level. Interface extends to another super interface by a level. Class implements interface and multiple inheritance is achieved indirectly which is otherwise not possible in a class.

Each interface created by a user has a unique data type with a combined effect of its data elements. Objects created in these classes uses interfaces also and each of these objects are the variables for interface data types.

Below example shows how classes implement interfaces, how objects of these classes are created linking the interfaces, and how they are executed.

// Sample program to demonstrate Interfaces interface Intface //Interface is defined < // It has its own data type public void dayname(); //Abstract method within the interface >class day1 implements Intface < // Class interacts through public void dayname() // interface implementation < // (each class is a variable for interface) System.out.println("Monday"); >> class day2 implements Intface < // Another class public void dayname() < System.out.println("Tuesday"); >> class day3 implements Intface < // Another class public void dayname() < System.out.println("Wednesday"); >> public class Subject < // Execution starts here public static void main(String[] args) < Intface t = new day1(); // Object of day1 class thru interface t.dayname(); // method invoked Intface tx = new day2(); // Object of day2 class thru interface tx.dayname(); Intface tx2 = new day3(); // Object of day3 class thru interface tx2.dayname(); >> // objects t, tx1, tx2 are the variables of // the interface data type

Conclusion

Class and interfaces are the major user-defined data types. Some forums have the opinion that String and Arrays are also part of user-defined types. Strictly speaking, they are part of standard data types of Java and hence they are not discussed.

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How to create a custom datatype in java?

Solution 4: You can’t create data types in java, but you can create object classes, like this: Solution 1: There are a few «options» in Java to express types, namely: interfaces, classes, and enums.

How to create a custom datatype in java?

I want to create an custom datatype in Java,for example datatype Email , that having following method isValidate(String email),isEmailExist(String email),getDomain(String email), get Id(String email),just like Integer class in java.

Integer is a class and I can initialise the object of integer class as follows:

I created my class Email and I want to initialise it as follows

How can i perform this functionality in my Email class.

import java.util.StringTokenizer; import java.util.regex.Matcher; import java.util.regex.Pattern; 
public class Email 
Email() < >public Boolean isvalid(String email)  
 
 
String lastToken = null; Pattern p = Pattern.compile(".+@.+\.[a-z]+"); // Match the given string with the pattern Matcher m = p.matcher(email); // check whether match is found boolean matchFound = m.matches(); StringTokenizer st = new StringTokenizer(email, "."); while (st.hasMoreTokens())
 
You cannot instantiate it as you write, the closest would be using a constructor:
 
Create an Email class. Java 101; any book or free tutorial of the Java language will get you started.
 
How can we create our own data type in java?, 4 Answers. There are a few "options" in Java to express types, namely: interfaces, classes, and enums. public class TwoByteHolder < public final …
 
Custom Data-type in Java
 
For an application I need to have an unsigned data-type with 24 bits. Unfortunately such a data type is not available in Java. I’m planning to implement it as a new class.But I’m not sure about the performance of such an implementation.
 
Is it advisable to write my own class?
 
If it is advisable, is it possible to good performance?
 
Presumably, you mean implement it as a class which uses a larger data type and bounds checking, like this:
 
public class Unsigned24 < private static final MAX_UNSIGNED24 = Math.pow(2, 24) - 1; private static final MIN_UNSIGNED24 = 0; private final int value; public Unsigned24(int value) < if (value >MAX_UNSIGNED24 || value < MIN_UNSIGNED24) throw new IllegalArgumentException("value out of bounds: " + value); this.value = value; >public int getValue() < return value; >// . other methods, such as equals(), comparison, addition, subtraction, etc. > 
 
This would work, but might not be worth the trouble. Also, it doesn't really take only 24 bits of memory, but rather 32 plus the overhead for an object.
 
It really depends on your goals. Why do you want a 24-bit integer.
 
Is it just because you have bounds-constraints on the values? If so, you might want to do something like the above.
 
Is it because you have a lot of them, and want to save memory? If so, you might want to build some class that abstracts an array of 24-bit integers, and internally saves them consecutively in a byte-array.
 
Is it because you are interfacing with some hardware or network interface that expects exactly 24 bits? In that case, you might want to look at the java.nio classes.
 
If you want to save space, you could use int for caluclation and map the least significant 3 bytes to a byte[] or just three bytes:
 
 public static byte[] convert(int i) < return new byte[]< (i & 0xff0000) >> 16, (i & 0xff00) >> 8, (i & 0xff) >; > public static int convert(byte[] b)
 
(can't verify if it is bug free but at least it should give an idea)
 
How to create a custom datatype in java?, That would make this question a not-so-beginner question after all. In Java this is noticeable when using the wrapper types. When you assign a literal …
 
How can we create our own data type in java?
 
I have a requirement where I have to create my own data type and i should assign some bytes to the data types. 
Example:
 
Datatype A : should have 1 byte of memory 
Datatype B : should have 2 bytes of memory 
Datatype C : should have 7 bytes of memeory etc..
 
Is there any way we can define our own data types and allocate some memory to them ?
 
There are a few "options" in Java to express types, namely: interfaces, classes, and enums.
 
In that sense, the best match would be a class, like:
 
public class TwoByteHolder
 
An object of that class allows you to exactly store 2 bytes; the next "level" could be something like:
 
But of course: the memory overhead would be enormous - Java isn't the the best language to deal with such requirements.
 
The only user-defined types available in Java are classes (including enums), and you cannot directly control how large they are. A class instance has many bytes of overhead you can't avoid having.
 
You can create a new class which has specific fields. If you need exact size of fields you can use byte arrays.
 
You can't create data types in java, but you can create object classes, like this:
 
Java - Initializing an array of custom type, 10. You need to use. Employee [] employeeArray = new Employee [3]; as well as add parentheses at the end of employeeArray [0].getEmployeeDetails …
 
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