Basic Java Knowledge

　After learning this long time of Java just started to feel very simple, but the logic is very strong behind, so still want to continue to refuel, the following is some basic things

Using the Eclipse tool

Write program basic naming

Class Name: Capitalize the first letter of each word

Variable name: The first word is all lowercase, other words are capitalized in the first letter

Variable name requirements: 1. Initials: Must be national language, underline and money

2. Other letters: first letter + number

Note: The initial value must be assigned before the variable is used

Auto Convert: 1. From small range to large range, automatic conversion

2. From large range to small range, cast

　　　3. Any type of "encounter" string, automatically converted to a string

judgment Equality: basic type with = =; Reference type with equals

Java Virtual machine principle:

Java is a Java Virtual machine (JVM) that installs a Java parser for any operating system. Write once and run everywhere.

Java cross-platform, virtual machines are not cross-platform, bytecode is run by the JVM.

Jvm:java Virtual Machine

Jre:java Runtime Environment  

Jdk:java Development Kit Java Development tools

Java Cross-platform principle:

The JVM itself is not cross-platform because there are different virtual machines on different platforms that interpret the same byte-code as a viable machine on different platforms

Code, so Java bytecode is a cross-platform

Java is really running a byte code (. Class) file

One. Java file, the file name must match the class name of the public class

One. Java file, you can use only one public class, but you may have more than one class

One or eight basic data types (native data types)

The largest of the numeric types is double, and the largest of all is string

Note: The following numbers represent the number of bytes

1.byte byte Type 1

2.short Short-Integer 2

3.int Integral Type 4

4.long Long Integer 8

5.float floating-point type (single precision) 4

6.double floating-point type (double precision) 8

7.char Character Type 2

8.boolean Boolean type 1/8

Ii. reference numeric type (object data type)

Other than the above eight data types are reference data types

The most common is the string

Basic Java Knowledge