Data Types in Java
Java Data types in a variable in Java must be a specified data type:
Example
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
In Java Data types are divided into two groups:
Primitive data types - includes byte, short, int, long, float, double, boolean and char
Non-primitive data types - such as String, Arrays and Classes (you will learn more about these in a later chapter)
Primitive Data Types
A primitive data type specifies the size and type of variable values, and it has no additional methods.
In Java , here are eight primitive data types in Java:
Numbers
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 byte, short, int and 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: float and double.
Integer Types
Byte
The byte data type can store whole numbers from -128 to 127. This can be used instead of int or other integer types to save memory when you are certain that the value will be within -128 and 127:
Long
The long data type can store whole numbers from -9223372036854775808 to 9223372036854775807. This is used when int is not large enough to store the value. Note that you should end the value with an "L":
Int
The int data type can store whole numbers from -2147483648 to 2147483647. In general, and in our tutorial, the int data type is the preferred data type when we create variables with a numeric value.
Example
int myNum = 100000;
System.out.println(myNum);
Example
long myNum = 15000000000L;
System.out.println(myNum);
Booleans
A boolean data type is declared with the boolean keyword and can only take the values true or false:
Example
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.
Characters
The char data type is used to store a single character. The character must be surrounded by single quotes, like 'A' or 'c':
Example
char myGrade = 'B';
System.out.println(myGrade);
Alternatively, you can use ASCII values to display certain characters:
Example
char a = 65, b = 66, c = 67;
System.out.println(a);
System.out.println(b);
System.out.println(c);
Floating Point Types
You should use a floating point type whenever you need a number with a decimal, such as 9.99 or 3.14515.
Float
The 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":
Example
float myNum = 5.75f;
System.out.println(myNum);
Double
The 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":
Example
double myNum = 19.99d;
System.out.println(myNum);
Use float or double?
The precision of a floating point value indicates how many digits the value can have after the decimal point. The precision of float is only six or seven decimal digits, while double variables have a precision of about 15 digits. Therefore it is safer to use double for most calculations.
Scientific Numbers
A floating point number can also be a scientific number with an "e" to indicate the power of 10:
Example
float f1 = 35e3f;
double d1 = 12E4d;
System.out.println(f1);
System.out.println(d1);
