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課程介紹
In programming, integers, floats, and doubles are called data types.
They are used to represent different kinds of numerical values.
Data type
What it stores
Example in Java
int
Whole numbers without decimal points
int age = 25;
float
Decimal numbers with single precision
float price = 9.99f;
double
Decimal numbers with double precision
double pi = 3.14159265;
In simple terms
-
Integer (int): Stores whole numbers, such as 10, -5, or 100.
-
Float (float): Stores decimal numbers, such as 3.14 or 7.5. In Java, you must add f at the end of a float literal, like 3.14f.
-
Double (double): Stores decimal numbers with greater precision than float. It is the default type for decimal literals in Java.
Java example
Remember: These are all primitive data types in Java.
Other primitive data types include byte, short, long, char, and boolean.
Java Data Types: A Beginner-
Friendly Lesson
Let's learn Java data types step by step, with simple explanations, examples, and practice exercises.
1. What are data types in Java?
A data type tells Java what kind of value a variable can store, such as a whole number, a decimal number, a character, or a true/false value.
Think of variables as boxes. Each box stores a particular kind of information, and the data type tells Java what kind of information belongs in that box.
int age = 20;
A box for a whole number.
double price = 19.99;
A box for a decimal number.
char grade = 'A';
A box for one character.
2. The two main categories of Java data types
Java data types are commonly divided into two categories.
A. Primitive data types
These are Java's eight built-in data types. They store simple values directly.
Type
Stores
Example
byte
Small whole numbers
byte n = 100;
short
Short whole numbers
short n = 1000;
int
Whole numbers
int n = 25;
long
Large whole numbers
long n = 900000L;
float
Decimal numbers
float n = 3.5f;
double
More precise decimals
double n = 3.14159;
char
One UTF-16 code unit
char c = 'A';
boolean
true or false
boolean b = true;
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