Basic program design structure of Java core technology 01:java

1. A simple Java application

 Public class Hello {        publicstaticvoid  main (string[] args) {        System.out.println ( "Hello world!" );    }}

Hello.java

2. Notes

• Line comment: From//start to end of bank
• Block Comment: Start with/* and end with */
• Document comments: Start with/** to */end

3. Data type

3.1. Integral type

Byte	1 bytes	-128 ~ 127
Short	2 bytes	-32768 ~ 32767
Int	4 bytes	-2147483648 ~ 2147483647
Long	8 bytes	-9223372036854755808 ~ 9223372036854755807

3.2. Floating-point types

Float	4 bytes	About ±3.40282347e+38f
Double	8 bytes	About ±1.79769313486231570e+308

3.3.char type

The char type is used to represent a single character (' A ').

3.4.booelan type

A Boolean (Boolean) type has only two values: True and False.

End.

Basic program design structure of Java core technology 01:java