Front end developers must read! Starting from scratch, teach you to build a low code website platform in stages>>> 
solutions to check out conflict with files in eclipse
Reference article:
(1) Solution of checkout conflict with files in eclipse
（2） https://www.cnblogs.com/fanblogs/p/10614335.html
Let’s make a note.
Eclipse Start Error: an error has occurred see the log file
Solution:
delete the temporary files of Eclipse: org.eclipse.osgi, org.eclipse.update in the eclipse/configuration directory
Restart eclipse
if not, back up the projects in the workspace, delete the workspace directory and the above two subdirectories
start eclipse again, and then import the backed up projects
Today, after updating the code from SVN, due to the use of base64encoder 
in the code
The following error is reported after updating: access restriction: the type ‘base64decoder’ is not API (restriction on required library’d:// Java/jdk1.7.0)_ 45\jre\lib\rt.jar’)
In fact, the solution is very simple. Just remove and add the JRE system library
Methods: right click the project – > Properties–> Java build path, switch to the libraries tab page, find the JRE system library, remove it, and then click add library – > Just add JRE system library. 
1. Right click the project – properties – Java build path – JRE system library – access rules – resolution and select accessible. Fill in * * below and click OK
2.When writing java code in MyEclipse, base64decoder, import sun. Misc. Base64decoder are used;
However, eclipse prompts: access restriction: the type base64decoder is not accessible due to restriction on required library c: (program files) \\\\\\\\\\\\\\\\\\\\\\\\
Solution 1 (recommended): just remove the JRE system library in the project build path, and then add the JRE system library. After recompiling, everything will be normal.
Solution 2: windows – > Preferences -> Java -> Compiler -> Errors/Warnings -> Deprecated and restricted API -> Forbidden reference (access rules): -> change to warning
After the project goes online, how to reduce customers’ doubts about the delivery?Here is the secret script of three moves>>> 
1、 Modify project attributes:
1
Right click the project in eclipse, select properties, and then select dynamic web module in project faces. Modify 3.0 to 2.3. You may be prompted with the following information:
cannot change version of project facet dynamic web module to 2.3
This means that you can’t modify it, and then use the second method
2、 Modify the configuration file:
find the hard disk directory of the project and open the. Setting folder under the project, as shown in the following figure:
Find the org.eclipse.wst.common.project.facet.core.xml file in the. Setting folder. The file format is as follows:
<?xml version=”1.0″ encoding=”UTF-8″?>
< faceted-project>
< fixed facet=”wst.jsdt.web”/>
< installed facet=”jst.web” version=”2.3″/>
< installed facet=”wst.jsdt.web” version=”1.0″/>
< installed facet=”java” version=”1.7″/>
</ faceted-project>
Manually modify the version corresponding to jst.web
Finally, restart Tomcat and you can use it normally
After the project goes online, how to reduce customers’ doubts about the delivery?Here is the secret script of three moves>>> 
eclipse Invalid project name: Project “xxx” already exists.
For some reason, I manually delete a project in the workspace, or because of an exception when creating a project, I can’t see the name of a project in eclipse, but if I create the same project again, it will be reported that the name is invalid, and the project XXX already exists
Invalid project name: Project “xxx” already exists.
We can go to the workspace to delete the project information of XXX under the project information path (workspace. Metadata. Plugins. Org. Eclipse. Core. Resources. Projects), and then refresh the Project Explorer. In this way, eclipse will automatically rebuild the following project space, and then there will be no project of XXX, You can recreate the project XXX
Saving path of project information opened by eclipse
workspace\.metadata\.plugins\org.eclipse.core.resources\.projects
After the project goes online, how to reduce customers’ doubts about the delivery?Here is the secret script of three moves>>> 
Today, after opening eclipse, eclipse is always in building workspace (sleeping). My solution is project – > Just shut down building automatically. Here are the other solutions I found on the Internet. There is no personal test
Eclipse has been building workspace perfect solution summary
1、 There are many reasons for this problem
1. Automatic upgrade 2, not closed correctly 3, Maven download lib hung, etc
2、 Solution summary
(1) Solutions
Method 1. Modify the eclipse startup file eclipse.ini and add the startup parameter: – vmargs – xmx512m
Method 2. Turn off auto build workspace: Project – > build Auto…..
Method 3. Add a command – clean in eclipse. Ini
(2) Increase the maximum memory available for eclipse operation
Specific operation: modify eclipse.ini in the eclipse directory, and increase – xmx512m, such as – xmx768m
(3) Reduce plug-ins that start automatically after eclipse starts
Specific operation: in preferences – > General -> Startup and shutdown: remove the excerpts of the items except plug ins activated on startup (for example, mylyn, etc. will be removed if they are not used)
Effect: after starting eclipse, there will be a scrollbar of initializing java tools, which is much faster
(4) Reduce the number of items that need to be verified during compilation, and improve the compilation speed
Specific operation: in preferences – > Validataion removes irrelevant validators, such as JPA, JSP and WS
Effect: when compiling projects, eclipse runs fewer validator projects, which is really fast
(5) Turn off automatic compilation
Specific operation: Project – > Build Automatically
Effect: after the code is modified and saved, automatic compilation will not be started
(6) When cleaning, pay attention to the options
Specific operation: Project – > Clean
Note: at the bottom are build the entire workspace and build only the selected projects
Check it according to your own situation, because it is the default to compile the entire workspace
(7) Display memory usage (manual GC is available)
Specific operation: preference – > General -> Show heep status
(8) Keep your perspective
Specific operations: 1. Window – > Save Perspective As
2. Preference -> Perspective -> Make default sets the perspective you just created or the one you often use as the default
(9) Turn off automatic publishing of server
Specific operation: server – > Publishing -> Never publish automatically
Access restriction : The type BASE64Decoder is not accessible due to restriction on required library C:\Program
files\java\jre6\lib\rt.jar
Access restriction : The constructor BASE64Decoder() is not accessible due to restriction on required library C:\Program files\java\jre6\lib\rt.jar
Solution 1 (recommended).
Just remove the JRE System Library in the project build path first, then add the library JRE System Library, recompile and everything will be fine.
Solution 2:
Windows -> Preferences -> Java -> Compiler -> Errors/Warnings ->
Deprecated and trstricted API -> Forbidden reference (access rules): -> change to warning
Specific details:
An internal error occurred during: “Building workspace”.
GC overhead limit exceeded
Analysis:
results
Solution:
The reason is that the default configuration memory of eclipse is too small. You need to change the eclipse.ini file in the eclipse installation folder
In other words, the default memory size of eclipse is not enough and needs to be modified
Open the directory where eclipse is located and find the eclipse.ini file. As shown in the figure below:
A289885427
open it with a text editor:
Change the values of the last two lines a little larger and add a line at the same time. The details are as follows:
-Xms1024m
-Xmx1536m
-XX:MaxPermSize=1024m
Restart eclipse after the modification. It’s normal
Parameter Description:
-What do the three parameters XMS/Xmx/- XX: maxpermsize mean
The figure is as follows:
Eclipse appears "The Eclipse executable launcher was unable to locate its companion shared library" error The solution is as follows: 1. Open the configuration file eclipse in the eclipse directory. ini. 2. Change the paths under --launcher.library and -startup to the current correct path. If the storage path of my eclipse is changed from D:\Program Files\ to D:\, just remove the "Program Files\" before eclipse in the path. If you want to display the working path dialog box when eclipse is opened, there are two solutions: Method one, close Eclipse and open the eclipse installation directory, open the following directories in turn, there is a file org.eclipse under the configuration\.settings folder. ui.ide.prefs, open with Notepad and change the following red characters to true: SHOW_WORKSPACE_SELECTION_DIALOG=true Method two, the setting method is as follows: open Window -> Preferences -> General -> Startup and Shutdown in turn. Then check the Confirm exit when closing last window check box. Or click the Restore Defaults button. ************************************************** ************************************************** ******* The following is more like your question: Taken from kiwi's garden's blog The Eclipse executable launcher was unable to locate its companion launcher jar To resolve this issue perform the following steps: Go to the installation location (for example, C:/Program Files/IBM/TeamConcert) Copy the eclipse.ini file to a backup file (such as eclipse.ini.bak). Edit the eclipse.ini file and remove these two lines: -startup plugins/ org.eclipse.equinox.launcher_1.0.100.v20080509-1800.jar Start the Rational Team Concert client again. Probably means to find eclipse.ini in the installation directory and remove the following two lines: -startup plugins\org.eclipse.equinox.launcher_1.0.100.v20080509-1800.jar
This is because the 64 bit JDK is installed, but the 32-bit eclipse is running. The problem can be solved by replacing one of the two
https://www.eclipse.org/downloads/packages/