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Lesson 4Examining Java's data types
ObjectiveUse data types to represent different types of information in Java.

Examining Java Data Types

Variables are locations in memory that are used to store information.
Java supports a variety of data types, which dictate the type of information that can be stored in a variable.
You create a variable in Java by specifying the type of the variable and an identifier that uniquely identifies the variable. Let us revisit an earlier example:

int age = 55;
String name = "Ernie";

The first line of code declares a variable named age whose data type is int, which is an integer (whole number) data type. The second line of code declares a variable named name whose data type is String, which holds text.
Both of these variable declarations set aside memory for each variable. The data type determines the amount of memory set aside.
For example, a Java int is a 32-bit number, so 32 bits of memory are set aside for an int variable.
Java data types can be grouped into two major categories:
  1. simple: a core data type that is not derived from any other type and represents a single piece of information (also called a primitive data type)
  2. composite: a data type based on simple types that is used to represent more complex information

Figure 6.4: Categorization of primitive Data Types

The simple (primitive) Java data types include
  1. Integer numbers,
  2. Floating-point numbers,
  3. booleans, and
  4. char Literal

  1. Integer numbers: Whole numbers without fractional parts (byte, short, int, long)
  2. Floating-point numbers: Numbers with fractional parts (float, double)
  3. Booleans: Values with one of two possible states: true or false
  4. Characters : Individual text characters (char)

Integral and Floating Point Types

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