Java must be a specified data type:
int myNum = 5; // Integer (whole number) float myFloatNum = 5.99f; // Floating point number char myLetter = 'D'; // Character boolean myBool = true; // Boolean String myText = "Hello"; // String
Data types are divided into two groups:
- Primitive data types – includes
- Non-primitive data types – such as String, Arrays and Classes (you will learn more about these in a later chapter)
Primitive Data Types
The size and type of variable values are specified by a primitive data type, which has no extra functions.
In Java, there are eight primitive data types:
|byte||1 byte||Stores whole numbers from -128 to 127|
|short||2 bytes||Stores whole numbers from -32,768 to 32,767|
|int||4 bytes||Stores whole numbers from -2,147,483,648 to 2,147,483,647|
|long||8 bytes||Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807|
|float||4 bytes||Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits|
|double||8 bytes||Stores fractional numbers. Sufficient for storing 15 decimal digits|
|boolean||1 bit||Stores true or false values|
|char||2 bytes||Stores a single character/letter or ASCII values|
Primitive number types are divided into two groups:
Integer types stores whole numbers, positive or negative (such as 123 or -456), without decimals. Valid types are
long. Which type you should use, depends on the numeric value.
Floating point types represents numbers with a fractional part, containing one or more decimals. There are two types:
Despite the fact that Java has multiple numeric types, the most commonly used for numbers are int (for whole numbers) and double (for floating point numbers).
However, as you read on, we’ll go through each one in detail.
From -128 to 127, the byte data type can hold entire values.
When you know the value will be between -128 and 127, you can use this instead of int or other integer types to conserve memory:
byte myNum = 100; System.out.println(myNum);
short data type can store whole numbers from -32768 to 32767:
short myNum = 5000; System.out.println(myNum);
Whole numbers between -2147483648 and 2147483647 can be stored in the int data type. When creating variables with a numeric value, the int data type is the ideal data type in general and in our course.
int myNum = 100000; System.out.println(myNum);
From -9223372036854775808 to 9223372036854775807, the long data type can store entire numbers. When int is insufficient to store the value, this is utilized. It’s important to note that the value should conclude with a “L”:
long myNum = 15000000000L; System.out.println(myNum);
Floating Point Types
When you need a decimal number, such as 9.99 or 3.14515, you should use a floating point type.
float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an “f”:
float myNum = 5.75f; System.out.println(myNum);
double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note that you should end the value with a “d”:
double myNum = 19.99d; System.out.println(myNum);
Is it better to use float or double?
The precision of a floating point value is the number of digits following the decimal point that the value can have.
The precision of float variables is just six or seven decimal digits, but the precision of double variables is around 15 digits.
As a result, for most calculations, it is safer to utilize double.
A floating point number can also be a scientific number with an “e” to indicate the power of 10:
float f1 = 35e3f; double d1 = 12E4d; System.out.println(f1); System.out.println(d1);
A boolean data type is declared with the
boolean keyword and can only take the values
boolean isJavaFun = true; boolean isFishTasty = false; System.out.println(isJavaFun); // Outputs true System.out.println(isFishTasty); // Outputs false
Boolean values are mostly used for conditional testing, which you will learn more about in a later chapter.
char data type is used to store a single character. The character must be surrounded by single quotes, like ‘A’ or ‘c’:
char myGrade = 'B'; System.out.println(myGrade);
Alternatively, you can use ASCII values to display certain characters:
char myVar1 = 65, myVar2 = 66, myVar3 = 67; System.out.println(myVar1); System.out.println(myVar2); System.out.println(myVar3);
String data type is used to store a sequence of characters (text). String values must be surrounded by double quotes:
String greeting = "Hello World"; System.out.println(greeting);
Because the String type is so widely utilized and integrated in Java, it is sometimes referred to as “the special ninth type.”
Because it relates to an object, a String in Java is a non-primitive data type. Methods on the String object are used to execute various operations on strings.
Non-Primitive Data Types
Because they refer to things, non-primitive data types are termed reference types.
The following are the fundamental distinctions between primitive and non-primitive data types:
- In Java, primitive types are predefined (that is, they have already been declared).
Java does not specify non-primitive types, which are constructed by the programmer (except for String).
- Non-primitive types, on the other hand, can be used to call methods that perform specific actions, whereas primitive types cannot.
- Non-primitive types can be null, whereas primitive types always have a value.
- A lowercase letter begins a primitive type, while an uppercase letter begins a non-primitive type.
- A primitive type’s size is determined by the data type, whereas non-primitive types are all the same size.
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