First knowledge of Java

# I. Tasks of this chapter

Writing HelloWorld Programs

Print console Information

# II. Objectives of this chapter

Installation and configuration of JDK

will use Notepad to develop a simple Java program

Outputs the information in the console using the output statement

Familiar with MyEclipse development environment

# Iii. Installationof JDK

# # (i) download of JDK

: http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

# # (ii ) Installing the JDK

Slightly

# # (iii ) Configuring the JDK

-Path

-Java_home

# # (iv ) verifying JDK

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-80cb59c173e17f03.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# Iv. Development of the first Java program

# # (I ) steps

-Source Code

-Compile

-Run

# # (ii ) Preparation of HelloWorld procedures

# # 1. Writing source code

Command line: Notepad

"' Java

public class helloworld{

public static void Main (string[] args) {

System.out.print ("Hello World");

}

}

```

Attention:

-The file name must be: HelloWorld

-Suffix name of file:. java

# # 2. Compiling

Javac

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-3a444f1f0481ffdb.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

Note: The file name after Javac must include the suffix name (. java)

Successful identification:

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-259d2ab40ae2a8f4.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 3. Run

Java

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-bfdd3f8135aebac4.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

* * Note: The file suffix name is not required after Java * *

# # (iii ) Understanding the structure of Java programs

# # 1. Structure

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-42b7852be5ae350b.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Output Statement

-System.out.print () No Line break

```

public class helloworld{

public static void Main (string[] args) {

System.out.print ("Hello World");

System.out.print ("Very hot Today");

}

}

```

* * Operation Effect: * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-9a665541c1ac4a1f.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

-System.out.println () line break

```

public class helloworld{

public static void Main (string[] args) {

System.out.println ("Hello World");

System.out.println ("Very hot Today");

}

}

```

* * Operation Effect: * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-b842753ec89057eb.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # (iv ) escape characters: \ t and \ n

# # 1. Meaning

! [] (http://upload-images.jianshu.io/upload_images/5818381-c10589c00bf64a75.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Example

-\ n

```

public class helloworld{

public static void Main (string[] args) {

System.out.print ("Hello world\n");

System.out.println ("Very hot Today");

}

}

```

* * Operation Effect * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-028ab536edce944d.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

-\ t

```

public class helloworld{

public static void Main (string[] args) {

System.out.print ("Hello world\t");

System.out.println ("Very hot Today");

}

}

```

* * Operation Effect * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-984a6794e9a7b650.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # (v ) Small examples of printed output

# # 1. Demand

! [] (http://upload-images.jianshu.io/upload_images/5818381-f3a0e5af8f7e7474.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

! [] (http://upload-images.jianshu.io/upload_images/5818381-70d9e009bb697986.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Reference Code

```

public class showinfo{

public static void Main (string[] args) {

System.out.println ("Name: Zhang San");

System.out.println ("Age: 18");

}

}

```

* * Program Run Effect * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-2758a0489711066a.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

```

public class showinfo{

public static void Main (string[] args) {

System.out.print ("Zhang San \ t");

System.out.print ("18");

}

}

```

* * Operation Effect: * *

! [] (http://upload-images.jianshu.io/upload_images/5818381-2a030bd94594d045.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # (vi) Comments for Java

For the convenience of others to read the program

Comments are not executed

# # 1. Single-line comment

# # # syntax

```

//

```

# # # example

```

public class helloworld{

public static void Main (string[] args) {

This is the newline output.

System.out.println ("Hello World");

System.out.println ("Very hot Today");

}

}

```

Program Run Results

! [] (http://upload-images.jianshu.io/upload_images/5818381-5c33bbebf50926e2.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

* * Note: Comments will not be executed * *

# # 2. Multi-line comments

# # # syntax

```

/*

Comment Content

*/

```

# # # example

```

public class helloworld{

/*

This is the entrance to the program.

This is a test multi-line Comment

*/

public static void Main (string[] args) {

This is the newline output.

System.out.println ("Hello World");

System.out.println ("Very hot Today");

}

}

```

# # 3. Document Comments

# # # syntax

```

/**

*/

```

# # (vii) Java Coding Specification

! [] (http://upload-images.jianshu.io/upload_images/5818381-44b406900b91e8fb.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

! [] (http://upload-images.jianshu.io/upload_images/5818381-1928d72a77a2e3ac.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# v. Development of Java programs using MyEclipse

# # (i ) download

Baidu

# # (ii ) crack

Reference Tutorials

# # (iii) MyEclipse steps to create a Java project

! [] (http://upload-images.jianshu.io/upload_images/5818381-f7fd91d36f0229ea.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 1. Create a Java project

! [] (http://upload-images.jianshu.io/upload_images/5818381-efff771442e9f842.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

Create a successful style

! [] (http://upload-images.jianshu.io/upload_images/5818381-a89d31b6d92777b7.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Creating and writing Java source programs

! [] (http://upload-images.jianshu.io/upload_images/5818381-64190bf6ff593884.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

! [] (http://upload-images.jianshu.io/upload_images/5818381-5341aa98181b932d.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 3. Compiling and running

Compile auto-complete

Run

! [] (http://upload-images.jianshu.io/upload_images/5818381-49bb8a4eb9d3c760.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # (iv) Java Project organizational structure

# # 1. Navigation view

! [Paste_image.png] (http://upload-images.jianshu.io/upload_images/5818381-d3cc24c79754e530.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # # Directory Description

! [] (http://upload-images.jianshu.io/upload_images/5818381-4e299ab27dda9555.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

-Bin: Store the compiled file

-SRC: Storage source program

# # 2. Package View

Package: Equivalent to a folder, in a different package, can have the same name code file

# # (v ) Several common errors in writing Javat programs

# # 1. The public decorated class name must be the same as the file name

! [] (http://upload-images.jianshu.io/upload_images/5818381-beb6ef044fc3e5e7.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Main method as the entry of the program, Void is necessary

! [] (http://upload-images.jianshu.io/upload_images/5818381-1b6bb6ef3d03ecd3.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 3. Java is case sensitive

! [] (http://upload-images.jianshu.io/upload_images/5818381-0a4bba84255c6b8a.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 4. Each Java statement must end with a semicolon

! [] (http://upload-images.jianshu.io/upload_images/5818381-7ca6e8653e3a5853.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 5. quotation marks necessary

! [] (http://upload-images.jianshu.io/upload_images/5818381-de7a4052ff76caee.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # (vi ) case

# # 1. Demand

! [] (http://upload-images.jianshu.io/upload_images/5818381-4ef35ff1eaee3bd9.png?imageMogr2/auto-orient/strip% 7cimageview2/2/w/1240)

# # 2. Reference Code

```

public class Showuserinfo {

public static void Main (string[] args) {

System.out.println ("Hello, I am a bluebird student");

System.out.println ("Name: Harry");

System.out.println ("Age: 18");

System.out.println ("Hobby: Playing basketball");

}

}

```

This article is from the "Master" blog, please keep this source http://imentors.blog.51cto.com/10946447/1952944

First knowledge of Java