Data Types II Concepts

Data Types II

In addition to the previous article on data types (please read it before you read this one), data types come in all different forms, shapes and sizes. In Java there are two different sections of data types - Primitive and Non-Primitive. Non-Primitive types are types that can usually hold other data types or multiple of the same data type.

Data Type Diagram in Java

As shown above the non-primtive data types include Arrays, Strings, Enums, Objects and Classes

Arrays
Strings
Enums

We will be looking at the above types in a bit more detail. The other non-primitive data types; Objects and Classes, are explained in the Objects, Classes and Methods article.

Arrays

An Array is a group of like-typed variables that are referenced to by a common name. Arrays in Java work differently than they do in C/C++.

Java Arrays are dynamically allocated, are technically objects, 0 indexed (IE they begin at the 0th position). It can also be used as a static field, local variable or a method parameter.

                        
                            int myArray[] = new int[20];
int myArray2[] = {2,4,6,7};

Above is how you declare an array, there are more ways to declare them as well. The first declaration involves instantiating the array and stating that it has 20 spaces, the array, is also identified as an int array which means that it is an array of integers. There are different types of arrays, such as string arrays, double arrays, short arrays etc. There are other types of lists you can import into Java which we may cover in the future.

Strings

Strings are widely used in Java programming. They are a sequence of characters, in Java they are treated as objects. They are also a Class but in other programming languages they are its own data type.

                        
                            String myString = "hi there I am a string";
System.out.println(myString);

//output: hi there I am a string

Making string is simple, they are denoted by the two double quotes around what you want to be enclosed in the string. You can manipulate strings by using regex patterns on them and matches, you can also convert them into other objects and data types, such as integers. You can also get the length of a string, by using string.length(). All of these methods can help you make a good cohesive Java program.

Enums

Enums are a special "class" that represents a group of constants. These are unchangeable, like final variables.

To create a enum, use the enum keyword, and separate the constants with a comma. Note that they should be in uppercase letters:

                        
                            enum Height{
    LOW,
    MEDIUM,
    HIGH
}

Height myHeight = Height.LOW;
System.out.println(myHeight);

// output: LOW

Enums are short for "enumerations" which means "specifically listed"

Sources: (click on them to see them)