boolean Data Type
In Java, the
boolean primitive data type is used to store a value, which can be either
boolean result = true; boolean isMarried = false;
A String in Java is a Object that holds multiple characters. It is not a primitive datatype.
A String can be created by placing characters between a pair of double quotes (
To compare Strings, the
equals() method must be used instead of the primitive equality comparator
// Creating a String variable String name = "Bob"; // The following will print "false" because strings are case-sensitive System.out.println(name.equals("bob"));
int Data Type
In Java, the
int datatype is used to store integer values. This means that it can store all positive and negative whole numbers and zero.
int num1 = 10; // positive value int num2 = -5; // negative value int num3 = 0; // zero value int num4 = 12.5; // not allowed
char Data Type
char is used to store a single character. The character must be enclosed in single quotes.
char answer = 'y';
Primitive Data Types
Java’s most basic data types are known as primitive data types and are in the system by default.
The available types are as follows:
null is another, but it can only ever store the value
int age = 28; char grade = 'A'; boolean late = true; byte b = 20; long num1 = 1234567; short no = 10; float k = (float)12.5; double pi = 3.14;
In Java, the type of a variable is checked at compile time. This is known as static typing. It has the advantage of catching the errors at compile time rather than at execution time.
Variables must be declared with the appropriate data type or the program will not compile.
int i = 10; // type is int char ch = 'a'; // type is char j = 20; // won't compile, no type is given char name = "Lil"; // won't compile, wrong data type
The value of a variable cannot be changed if the variable was declared using the
Note that the variable must be given a value when it is declared as
final variables cannot be changed; any attempts at doing so will result in an error message.
// Value cannot be changed: final double PI = 3.14;
double Data Type
double primitive type is used to hold decimal values.
double PI = 3.14; double price = 5.75;
Basic math operations can be applied to
float data types:
%modulo (yields the remainder)
These operations are not supported for other data types.
int a = 20; int b = 10; int result; result = a + b; // 30 result = a - b; // 10 result = a * b; // 200 result = a / b; // 2 result = a % b; // 0
Comparison operators can be used to compare two values:
>=greater than or equal to
<=less than or equal to
!=not equal to
They are supported for primitive data types and the result of a comparison is a boolean value
int a = 5; int b = 3; boolean result = a > b; // result now holds the boolean value true
Compound Assignment Operators
Compound assignment operators can be used to change and reassign the value of a variable using one line of code. Compound assignment operators include
int number = 5; number += 3; // Value is now 8 number -= 4; // Value is now 4 number *= 6; // Value is now 24 number /= 2; // Value is now 12 number %= 7; // Value is now 5
Increment and Decrement Operators
The increment operator, (
++), can increase the value of a number-based variable by
1 while the decrement operator, (
--), can decrease the value of a variable by
int numApples = 5; numApples++; // Value is now 6 int numOranges = 5; numOranges--; // Value is now 4
Order of Operations
The order in which an expression with multiple operators is evaluated is determined by the order of operations: parentheses -> multiplication -> division -> modulo -> addition -> subtraction.
Casting is the process of transforming a value of one primitive data type to another.
double value can be transformed into an
int value using the
(int) casting operator, while an
int value can be transformed into a
double value using the
(double) casting operator.
// Convert double to int double numDouble = 12.99; System.out.println((int)doubleNum); // Prints: 12 // Convert int to double int numInt = 9; System.out.println((double)numInt); // Prints: 9.0