Java Review (i)

Java Development Environment Building

1. Download JDK

2. Environment variable Configuration

3. Enter Java-version in DOS

Java Run process

Source file: Write source file, suffix. java

Compile: Compile the source file into a bytecode file with a. class suffix.

Run: Run a bytecode file with the interpreter

The first Java program

Output Hello world!

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

Output:

Key words

Identifier

1, can only be composed of numbers, letters, $, _

2. Cannot start with a number, first letter, case-sensitive

Data types and Constants

Constants: The amount of unchanging data

5: Integer Constants

True: Boolean Constants

5, 5: floating-point constants

S: Character constants

Binary, octal, decimal, hexadecimal

Binary: Digital start plus 0B

Octal: Number start plus 0

Decimal: No need to add

Hex: Number starts with 0X

Comments

Single-line Comment://

Multiline Comment:/* */

Document Comment:/**/

Java Review (i)