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Java Data Types

Data types are devided into two groups

• primitive : byte, short, int, long

  • float, double

  • boolean, char

• Non-primitive : String, Arrays, Classes

Primitive Data Type

The type specifies the size and type of variable value

It has no additional method

8 primitive data type in Java

• interger(store whole) : byte(1byte) < short(2bytes) < int(4bytes) < long(8bytes)

• floating point(store fractional) : float(4bytes) < double(8bytes)

  • sufficient for storing 6~7 / 15 decimal digit

• boolean(1bit) : store true o false

• char(2bytes) : store a single character/letter or ASCII

• * Scientific number

  • “e” indicate the power of 10

  • “12E3” means “12000”

• * Alternatively can use ASCII value

  • char var = 65; output “A”

Non-primitive Data Type

called reference type(they refer to object)

The main different between Non-primitive and primitive

Java type Casting

assign a value of one primitive data type to another

• Widening casting(automatically) : converting a smaller to large

  • byte < short < char < int < long < float < double

• Narrowing casting(manually)

  • must be done manually by placing the type in parentheses in front of the value

double d = 9.78d;
int i = (int)d;