1 Learning Insights

1.1 Why learn java

java can do desktop applications, such as banking software, shopping mall settlement software; develop Internet-oriented applications, such as online digital malls, Alibaba and eBay, etc.

1.2 Confused

There is so much java content, can't you learn it?Are there so many scenes?Can't hold on?How to break?

1.3 Principles

At the beginning of learning, do not entangle with the scene, do not entangle with the principle; language comes from life, programming also comes from life, the first thing we have to do is not to prepare various software, but to integrate ourselves into a program firstin the minds of members.
What can be explained in life, the code must be written; the code that cannot be explained, the code must not be written.
Don't be hesitant, don't be confused, if you have any questions, please ask the classmates in the surrounding clubs.Persevere to the end, and you will surely reap the rewards.

1.4 Language Sense

Not at the beginning, through a lot of practice and accumulation process

1.5 How to Learn

Copy first, understand the requirements, and then without looking at the source code, you can write those small demos by yourself. In the final analysis, it is just four words: write more, think more.

2 Java Environment Construction

2.1 Download and install JDK

Notes:

1. Select version 1.7/1.8 (software development, the more stable the better, not the newer the better)
2. JDK installation select the corresponding system type 32/64 operating system
3. There cannot be Chinese characters and special characters between the paths

2.2 Configuring environment variables

2.2.1 Configuring JDK

Take win7 as an example:

JAVA_HOME:localJDK installation path
CLASSPATH: %JAVA_HOME%\lib;%JAVA_HOME%\lib\tools.jar;
PATH: %JAVA_HOME%\bin;%JAVA_HOME%\jre\bin;

2.2.2 java program in three steps

2.2.3 java virtual machine and cross-platform principle

3 Java Coding Specifications

3.1 escape characters

\t : move the cursor to the first cell of the next line
\n: move the cursor to the next horizontal tab position
\r: return the cursor position to the beginning of the line

3.2 Coding Conventions

1. Write one sentence in one line
2. Pay attention to indentation
3. Pay attention to capitalization
4. All symbols are half-width in English

4 data types

4.1 8 basic data types

Where: In java, the default type of integer is int type, and the default type of floating point type is double type

4.2 Variable Naming Rules

1. Word (letter), underline (underscore), beauty (dollar sign), person (RMB sign), number (number), camel (camel case)
2. Meaningful
3. Cannot use keyword: publicclass
4. The first letter of the variable name is lowercase
5. In the same code block: the variable name cannot be declared repeatedly
6. Boolean type
7. Character type
8. Constant: inAdd final
before the statement 9. Naming rules: all letters are capitalized, and words are separated by underscores

5 Type Conversion

5.1 Type Conversion Rules

1. The short one can be directly put into the long one
2. The long one cannot be directly put in the short one, it needs to be converted
3. The low precision can be directly converted to high precision
4, high precision cannot be directly converted to low precision, it needs to be forced to be converted