Java Fundamentals (ii)

Iv. data Types for Java

Basic data type: 8 kinds of Primitive.

1. Integral type

BYTE 1b 8-bit-128 to 127

Short 2b 16-bit -2^15 to (2^15)-1

INT 4b 32-bit -2^31 to (2^31)-1

Long 8b 64-bit -2^63 to (2^63)-1

2, floating-point type

FLOAT 4b 32-bit

Double 8b 64-bit

3. Character type

Char 2b 16-bit

4. Boolean type

Boolean flase/true

Note:

1. Automatic type promotion problem in Java

Forward procedure: From low to high bytes can be automatically converted.

Byte-->short-->int-->long-->float-->double

Reverse process: Convert from high byte to low byte with coercion type.

Note: Reverse conversion will lose precision

2. Boolean: Only True and False

3, Char:java with "\u four hexadecimal digits (even if \u appear in the note, followed by an error if not 4 digits)" means converting characters to their corresponding Unicode encodings, and character types enclosed in single quotes.

4. The default floating-point type has a suffix of "f" or "F" for the Double,float data type.

5. The long type has a suffix of "l" or "L".

Class, interface, array

　　Reference type variable name = new reference type name (parameter);//new half followed by the constructor of the class

Member: Written in parentheses inside the body of the class

Automatic type promotion:

BYTE A=1;

BYTE b=2;

A=a+b; Compilation error automatic type promoted to int

A+=b; Z Self-add no automatic type promotion

Type automatic promotion rules:

A and B do some sort of arithmetic:

A and B have double, the result is double

A and B have float, the result is float

A and B have a long, the result is long

In addition, the result is int.

Converting a high byte to a low byte requires a forced type conversion;

byte c= (byte) a+b;

Java Fundamentals (ii)