01day_java Basic Syntax

1. Java Development Environment Overview

Jdk:java Development Kit (Java Development Kit), including Java compilers, Java Runtime Environments, and commonly used class libraries;

Jre:java Runtime Environment (Java Runtime Environment).

2. Cross-platform features

① platform refers to the operating system (WINDOWS,LINUX,MAC)

②java programs can be run on any operating system, once written and run everywhere

③ implementing a Java-dependent virtual machine JVM for cross-platform use (Java virtual machines)

3. Setting of Environment variables

JAVA_HOME:JDK Path

Path: Add%java_home%\bin;

Input JAVAC-VERIOSN Test succeeded

4. Successfully compiled and run, output Hello world!

5. Use Advanced Notepad notepad++

6. Comments

Role: Explanatory notes, easy to read

Single-line Comment://I am a comment

Multiline Comment:/* I am comment */

Document Comments:/** comments */

7. Key words

The keywords in Java are lowercase

8. Identifiers

Composition rules: Letters 52 A-Z, a-Z, number 0-9, underscore (_), dollar sign ($), cannot start with a number, cannot be a keyword

Class Name: First Capital, first letter of the second word

Method Name: First letter lowercase, each word capitalized

9. Data

program = data + logic

Data type: base data type, reference data type (array, class, interface)

10. Constants

Integer type:

Decimal: The numbers that are often in life

Binary: Start with 0b, such as 0b1001;

Hex: Starting with 0x, the number is composed of 0-9 and a-f, such as 0xa;

Octal: Starting with 0, such as 07

Decimal type:

such as 1.0

Boolean type:

True, False

Character type:

Characters must be enclosed in single quotes and can contain only one character;

String constants:

String type is a reference type and must be wrapped in double quotation marks, which can contain 0-n characters.

01day_java Basic Syntax