Summary of exceptions and packages during java development

This article mainly introduces exceptions and packages in the basics of java. Friends in need can refer to it

1 Exceptions

Exception system

• Throwable

Error

# Usually major problems occur, such as: the running class does not exist or memory overflows, etc.

Do not write code to handle it

Exception

Occurs at runtime In this case, you can use try catch finally

The subclass names of Exception and Error are suffixed with the parent class name.

1.1 Methods in Throwable

##1.2 throws and throw

1.3 Exception handling

try
{
需要检测的代码；
}
catch(异常类
变量)
{
异常处理代码；
}
finally
{
一定会执行的代码；
}

Inherit Exception or its subclasses.

constructor .

Example:

Class DemoException extends Exception
{
　　DemoException(String message)
　　{
　　　　super(message);
　　}
}

1.5 Exception details

Category management of class files.

Provide multiple layers of

to classes.
is written on the first line of the program file.

The full name of the class name is package name.class name.

Package is also a form of encapsulation.

The class permissions in the accessed package must be public.

Member permissions in a class: public or protected

protected is a permission provided to subclasses in other packages

Routine

##3 import

4 Jar package

4.1 Operation of Jar package

Through jar. The operation of jar by exe tool.

jar -cvf mypack.jar packa packb

jar -tvf mypack.jar [>Directed file]

jar -xvf mypack.jar

jar –cvfm mypack.jar mf.txt packa packb

Java Free Video Tutorial

2. YMP Online Manual

3. Comprehensive analysis of Java annotations

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