I need to write a project that's only compatible with Java 1.5. I have Java 1.6 installed. Is there some form of backwards compatibility to get Eclipse to compile with 1.5?
Do I have to install Java 1.5 to get it to show here? Or maybe there is another way?
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Click on the Add Library button. It brings your screen to point to the Java location.
Select "Directory", button right besides JRE home and point to the installed folder location.
Even though you want to just 1.5 compiler project, you can achieve it by changing compiler settings in Eclipse instead of removing 1.6 JRE and add 1.5 JRE.
GOTO -->JAVA--Compiler---> and change compiler level to `1.5` instead of `1.6`
As davidfmatheson suggested,
Just be careful, especially if you're setting this up for a team of people to work on. If anyone uses anything that is new or changed in 1.6, it will compile, but not run in an environment with JRE 1.5.
Click on the Window tab in Eclipse, go to Preferences and when that window comes up, go to Java → Installed JREs → Execution Environment and choose JavaSE-1.5. You then have to go to Compiler and set the Compiler compliance level.
Right click project -> Properties -> Java Build Path -> select JRE System Library click Edit and select JDK or JRE after then click Java Compiler and select Compiler compliance level to 1.8
If you are using maven build tool then add the below properties to it and doing a maven update will solve the problem
<properties>
<maven.compiler.source>1.8</maven.compiler.source>
<maven.compiler.target>1.8</maven.compiler.target>
</properties>
In the preferences section under Java -> Installed JREs click the Add button and navigate to the 1.5 JDK home folder. Then check that one in the list and it will become the default for all projects:
Eclipse - specific Project change JDK Version -
If you want to change any jdk version of A specific project than you have to click ---> Project --> JRE System Library --> Properties ---> Inside Classpath Container (JRE System Library) change the Execution Environment to which ever version you want e.g. 1.7 or 1.8.
The JDK (JAVA_HOME) used to launch Eclipse is not necessarily the one used to compiled your project.
To see what JRE you can select for your project, check the preferences:
General → Java Installed JRE
By default, if you have not added any JRE, the only one declared will be the one used to launched Eclipse (which can be defined in your eclipse.ini).
You can add any other JRE you want, including one compatible with your project.
After that, you will need to check in your project properties (or in the general preferences) what JRE is used, with what compliance level:
(source: standartux.fr)
See the page Set Up JDK in Eclipse. From the add button you can add a different version of the JDK...
As I was facing this issue minutes ago, in case you are trying to open an existing project in an environment with a newer JDK, make sure you pdate the JDK version in Project Properties -> Project Facets -> Java.
Related
I have two JDKs, for Java 6 and 7.
I want to build my project using both. Initially we only built against 1.6.
I see in my project setting I can select 1.5, 1.6 1.7 as the compiler level.
How are these options added to the IDE? I never installed Java 1.5.
Suppose I wanted Java 1.4. How would I get this to appear in the list? I have added two different JREs in my IDE preferences, but these are not what appears in the dropdown.
You manage the list of available compilers in the Window -> Preferences -> Java -> Installed JRE's tab.
In the project build path configuration dialog, under the libraries tab, you can delete the entry for JRE System Library, click on Add Library and choose the installed JRE to compile with. Some compilers can be configured to compile at a back-level compiler version. I think that's why you're seeing the addition version options.
Some additional steps may be needed to set both the project and default workspace JRE correctly, as MayoMan mentioned. Here is the complete sequence in Eclipse Luna:
Right click your project > properties
Select “Java Build Path” on left, then “JRE System Library”, click Edit…
Select "Workspace Default JRE"
Click "Installed JREs"
If you see JRE you want in the list select it (selecting a JDK is OK too)
If not, click Search…, navigate to Computer > Windows C: > Program Files > Java, then click OK
Now you should see all installed JREs, select the one you want
Click OK/Finish a million times
Easy.... not.
To tell eclipse to use JDK, you have to follow the below steps.
Select the Window menu and then Select Preferences. You can see a dialog box.
Then select Java ---> Installed JRE’s
Then click Add and select Standard VM then click Next
In the JRE home, navigate to the folder you’ve installed the JDK (For example, in my system my JDK was in C:\Program Files\Java\jdk1.8.0_181\ )
Now click on Finish.
After completing the above steps, you are done now and eclipse will start using the selected JDK for compilation.
Configuring JDKs
Windows -> Preferences -> Installed JREs, to configured the installed JDKs
Project Properties, Java Compiler, Enable project specific settings (or configure Workspace settings), JDK Compliance
Project Properties, Java Build Path, Libraries, Add Library, JRE system library, Workspace default or Alternate JRE (one of the JREs configured in
Maven
BUT IF you are using maven, provided that you have your latest JRE (Windows/Preferences/Installed JREs) -for example JDK 1.8
You can select the level 1.6, 1.7, 1.8 by configuring the maven-compiler-plugin source and target attributes, like this
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
And ideally, if you have a parent pom, you can do it for all the modules (Eclipse projects) in the parent pom, in one single place.
Source and Target
If we want to use the Java 8 language features the –source should be set to 1.8. Also, for the compiled classes to be compatible with JVM 1.8, the –target value should be 1.8.
Updating JRE library that is broken in many projects at once (with Maven)
Rather than updating one by one the JRE library, let Maven do it for you.
Selecting the projects and right-clicking for Maven -> Update Project, will set the system library to the path of the installed JDK, in case the paths are broken (because you installed a new JDK or imported from another computer, etc.) and set the JDK compliance according to the maven source and target setting in the pom.
Eclipse's compiler can assure that your java sources conform to a given JDK version even if you don't have that version installed. This feature is useful for ensuring backwards compatibility of your code.
Your code will still be compiled and run by the JDK you've selected.
JDK 1.8 have some more enrich feature which doesn't support to many eclipse .
If you didn't find java compliance level as 1.8 in java compiler ,then go ahead and install the below eclipse 32bit or 64 bit depending on your system supports.
Install jdk 1.8 and then set the JAVA_HOME and CLASSPATH in
environment variable.
Download eclipse-jee-neon-3-win32 and unzip : supports to java 1.8
Or download Oracle Enterprise Pack for Eclipse (12.2.1.5) and unzip
:Supports java 1.8 with 64 bit OS
Right click your project > properties
Select “Java Compiler” on left and set java compliance level to 1.8
[select from the dropdown 1.8]
Try running one java program supports to java 8 like lambda
expression as below and if no compilation error ,means your eclipse
supports to java 1.8, something like this:
interface testI{
void show();
}
/*class A implements testI{
public void show(){
System.out.println("Hello");
}
}*/
public class LambdaDemo1 {
public static void main(String[] args) {
testI test ;
/*test= new A();
test.show();*/
test = () ->System.out.println("Hello,how are you?"); //lambda
test.show();
}
}
I installed Eclipse mars with java JDK8 but was was having lots of problems with it so I uninstalled it changed back to JDK7 and now I'm getting a strange compiler error in a few of my projects. I noticed that when I went into, Windows->Preferences-> Java->Installed JREs, there is an error message at the top saying that "The selected JRE does not support the ...rent compiler compliance level of 1.8" but when I check the compiler compliance level its set to 1.7
Ok so I decided to try starting a new project and when trying to build it a warning came up that my workspace compliance level was at level 1.8...changing the workspace fixed the problem. So new is it possible to change the workspace compliance level or should I just import my projects into a new workspace?
I tried importing into a new workspace,same problem. So I started new project in a new workspace, copyed and pasted the code in a voila it works! Very annoying if I have to do that for every class in every project I want.
Check your compliance settings in:
Preferences > Java > Compiler
Make sure the default is set to 1.7 as it may have defaulted to 1.8 after the initial install/run.
Also check project-specific compliance settings in:
(Project) Properties > Java Compiler
I changed Windows ->Preference->Java->Installed JREs to jdk1.7.0_79 and right clicked the project, Properties ->Java Build Path, made sure that under Libraries tab, it is JRE System Library[JavaSE-1.7]. Clicked Project ->Clean. Right clicked the project again, Properties ->Java Compiler, checked Use compliance from execution environment 'JavaSE-1.7' on the 'Java Build Path'.Then it worked.
If you already changed all settings to 1.7 (both in the eclipse preferences and the project properties) check your project's build path. How? Easy, after you've imported your project, right-button click it and select Build path > Configure Build Path. Then, check if you have your JRE system library correctly set.
If even this is set up ok, I would say that you probably have some code that can only be compiled by jdk 8 and you're trying to use jdk7 compliance level, which eclipse warns you about. An example of this is using lambda functions, which can only be compiled with java 8 as far as I know.
Go to Windows >> Preferences>>Compiler >> Unselect default
compliance settings >> select the compiler compliance level to 1.8
This should reflect in generated .class files compatibility
as 1.8 and source compatibility as 1.8 Step Step
Apply it Step
now click on apply and close
clean and build the project.
I have similar issue with Mars on Pydev environment. Seems that Mars want java jre 1.7.0, so for me was work by copy inside(create if not avaiable) eclipse\jre\ folder and copy the 1.7.0 version of jre inside
I have 3 versions of Java installed on my system: 6, 7, and 8... I am required to have JRE6 available for a product my company develops, so I cannot get rid of it... But despite copying my Eclipse install to a new folder for another project I need to work on and removing JRE6 from this version alltogether, I still cannot get it to work.
How can I get the google plugin for Eclipse to work in my scenario?
If you have created a shortcut to start eclipse, you can add a parameter to tell it to use the jre of your choice like this -
C:\eclipse\eclipse.exe -vm "C:\Programs\jdk\jdk1.7.0_55\bin\javaw.exe"
I have used "javaw" executable from a jdk installation, but you may point to the same executable within a JRE installation as well.
This will resolve the error.
Keep in mind that there is a separation between the JVM that Eclipse itself is running in and the various JREs that you can configure in Eclipse to run your programs/applications. You need to specify to Eclipse what JVM you want it to run under, using eclipse.ini.
That's separate from the Installed JREs configuration you show in your screen shot above.
Add Java 7.0 to Eclipse if you haven't: Window -> Preferences -> Java -> Installed JREs.
Next add Java 7.0 library to your project: Right click on project -> Properties -> Java Build Path -> Libraries tab -> Remove JRE 1.6 and add New Library (JRE System Library, 1.7.0).
Last set Java 7.0 compliance level: Right click on project -> Preferences -> Java Compiler -> Compiler compliance level: 1.7
Also since you can use different Java to run applications, you also have to change this in the Run configuration which you use to start AppEngine related tasks.
I am having some trouble updating the compiler compliance of my eclipse workspace (I am actually using RTC, but it is essentially eclipse).
Currently, it uses a jdk of 1.6 so I can change the JDK compliance to a limit of 1.6.
However, I am using jdk 1.7 for my project -I have added it as a JRE -
preferences --> Java --> Installed JRE --> added jre with the jdk 1.7 directory.
However, even though I use this as the default JRE it does not allow me to change the compiler compliance level to 1.7.
I am guessing that there is something I am missing.
Any help would be greatly appreciated
The Compiler compliance level is Version Dependent in eclipse. If you are using Eclipse 3.7 or lower then you won't get 1.7 compliance. Use Eclipse JUNO or higher.
For more on JDT Core 7 and its release related information
UPDATE:
Even eclipse 3.7.1 version supports Java 7 features and compliance level.
I use eclipse 3.6.1 with installed JRE 1.7 and I was able to set Java compliance level to 1.7 (on the workspace level - preferences).
In some workspaces I could do that right in the Preferences, in some workspaces I had to do that in a "hard way" updating several properties in the file:
.metadata\.plugins\org.eclipse.core.runtime\.settings\org.eclipse.jdt.core.prefs
Here are changed lines:
org.eclipse.jdt.core.compiler.compliance=1.7
org.eclipse.jdt.core.compiler.source=1.7
org.eclipse.jdt.core.compiler.codegen.targetPlatform=1.7
Maybe it was just enough to change the line with "org.eclipse.jdt.core.compiler.compliance" property , but I did all three for the sake of completeness and consistency.
If you are using eclipse 3.7 then you add 1.7 into compliance level by following way:-
right click on project
click on Build path->Configure Build Path->project Facets
there you can see one link 'convert to faceted form'. click on it
mark java and select verion 1.7 from dropdown which is present in front of java tab
click on apply and click ok
now you can see that 1.7 version is appeared in compliance level
Note:- Before above step you have to add JRE System library in Build path for jdk1.7
Right click on project you have in use, click on Properties,
enter image description here
go on "Compiler compilance level", and select 1.8
enter image description here
Select your project, then go to Project -> properties.
In Properties -> Java Compiler.
Under JDK Compliance if "use compliance from execution environment " is checked then uncheck it and you would see a dropdown in from of Compiler Compliance Level. Chose your desired version from here.
Click on Apply and Close.
Hopefully, this would resolve the issue.
It seems like this should be a simple task, with the options in the Preferences menu for different JREs and the ability to set different compiler and build paths per project. However, it also seems to simply not work.
For example, I have my JAVA_HOME set to a jre for Java 1.6. It's still not clear to me how Eclipse uses this, but it appears to be defaulting to this and not taking the project overrides. I have also installed Java 1.5, and added a JRE for this in eclipse in the Java->Installed JREs section.
In my project, I've set the compiler compliance level to 1.5. In the build path for the project, I've added the System Library for the Java 1.5 JRE. However, I'm getting compile errors for a class that implements PreparedStatement for not implementing abstract methods that only exist in Java 1.6 PreparedStatement. Specifically, the methods
setAsciiStream(int, InputStream, long) and
setAsciiStream(int, InputStream)
Strangely enough, it worked when we were compiling it against Java 1.4, which it was originally written for. We added the JREs for Java 1.4 and referenced that system library in the project, and set the project's compiler level to 1.4, and it works fine. But when I do the same changes to try to point to Java 1.5, it instead uses 1.6.
Any ideas why?
From the menu bar:
Project -> Properties -> Java Compiler
Enable project specific settings (checked)
Uncheck "use Compliance from execution environment '....
Select the desired "compiler compliance level"
That will allow you to compile "1.5" code using a "1.6" JDK.
If you want to acutally use a 1.5 JDK to produce "1.5" compliant code, then install a suitable 1.5 JDK and tell eclipse where it is installed via:
Window -> preferences -> Installed JREs
And then go back to your project
Project -> properties -> Java Build Path -> libraries
remove the 1.6 system libaries, and:
add library... -> JRE System LIbrary -> Alternate JRE -> The JRE you want.
Verify that the correct JRE is on the project's build path, save everything, and enjoy!
Eclipse uses it's own internal compiler that can compile to several Java versions.
From Eclipse Help > Java development user guide > Concepts > Java Builder
The Java builder builds Java programs using its own compiler (the Eclipse Compiler for Java) that implements the Java Language Specification.
For Eclipse Mars.1 Release (4.5.1), this can target 1.3 to 1.8 inclusive.
When you configure a project:
[project-name] > Properties > Java Compiler > Compiler compliance level
This configures the Eclipse Java compiler to compile code to the specified Java version, typically 1.8 today.
Host environment variables, eg JAVA_HOME etc, are not used.
The Oracle/Sun JDK compiler is not used.
First off, are you setting your desired JRE or your desired JDK?
Even if your Eclipse is set up properly, there might be a wacky project-specific setting somewhere. You can open up a context menu on a given Java project in the Project Explorer and select Properties > Java Compiler to check on that.
If none of that helps, leave a comment and I'll take another look.
Just to clarify, do you have JAVA_HOME set as a system variable or set in Eclipse classpath variables? I'm pretty sure (but not totally sure!) that the system variable is used by the command line compiler (and Ant), but that Eclipse modifies this accroding to the JDK used