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
Related
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
how can I make Java programs in Java 6 rather than Java 7 or 8, so that most machines can run my programs. Do I download a separate JDK? Do I change the compiler's compliance level? Or do I download a separate JRE. I am very confused, and I really need help.
Thank you so much!
Oh and I am using the IDE Eclipse.
If compiling from the command line, it can be done by using the following.
javac -source 1.6 -target 1.6 (files)
Eclipse uses its own java compiler. In the Eclipse IDE, go to Window > Preferences > Java > Compiler, and change the Compiler compliance level. 1.8 is for Java 8, select 1.6 if you need Java 6. Preferences are global for all java projects of your workspace.
If you want a specific configuration you can untick Use default compliance settings (if not already unticked), and change Generated .class files compatibility and Source compatibility separately.
If you'd like to make the change just for the current project, go to Project > Properties > Java Compiler, tick Enable project specific settings (if not already ticked), then as before, set the compiler configuration to what you need.
You should download JDK 6 on your system and point Eclipse to use it.
However if you are using command line, then there is no difference in How you compile it,
To Compile
javac FileName.java
To Run
java ClassName
FYI
JDK is the Java Development Kit, which has all the tools to do Java development.
JRE is Java RunTime Environment, which has Java's libraries and JVM which can run the Java programs.
In simple words you can say, to develop Java code you need JDK but if you ONLY want to run it, then you will be done only with JRE.
Eclipse IDE has its own java compiler. You can set the "compiler compiance level" from the preferences: (Menu > Windows > Preferences)
"1.8" is Java 8...
Preferences are global for all java projects of your workspace.
It is also possible to define it for each java project (context menu > properties) on the project.
In Eclipse, Go to Window > Preferences > Java > Compiler and you can select 1.6 as the compliance level.
I'm using Eclipse 3.3. In my project, I've set the compiler compliance level to 5.0 In the build path for the project. I've added the Java 1.5 JDK in the Installed JREs section and am referencing that System Library in my project build path. 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 5.0, it instead uses Java 6.
Any ideas why?
I wrote a similar question earlier, here:
how do I get eclipse to use a different compiler version for Java?
I know how you're supposed to choose a different compiler but it seems Eclipse isn't taking it. It seems to be defaulting to Java 6, even though I have deleted all Java 6 JDKs and JREs that I could find. I've also updated the -vm option in my eclipse.ini to point to the Java5 JDK.
This isn't about the compiler - it's only about the library! Go to the project's properties, then under Java Build Path / Libraries, remove the JRE System library. Then use Add Library... to add the version of the JRE library you want.
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
In Java 1.5, to deprecate a method you would:
#Deprecated int foo(int bar) {
}
Compiling this in Java 1.6 results in the following:
Syntax error, annotations are only
available if source level is 1.5
Any ideas?
You have to tell the compiler to use 1.6:
javac -source 1.6
Or equivalent for your IDE/build system (as others have suggested).
First, its #Deprecated, and second - double-check if you are really compiling with Java 1.6. What are you using? javac? Eclipse?
If using javac, make sure your JAVA_HOME is set to point to JDK 6, not JDK 1.4.2
If using Eclipse (or any IDE), right click the project > properties > and search for compiler level.
Syntax error, annotations are only available if source level is 1.5
This is a typical IDE error message. You've configured the workspace or the project to use compliance level 1.4 or older. Assuming that it's Eclipse (it's at least recognizeable as an Eclipse error), then you need to go to Java > Compiler in workspace preferences and set the Compiler compliance level to 1.5 or newer. You need to check this in the Java Compiler entry in Project's properties as well.
If you are using Eclipse IDE then
1- Select your project in Project Explorer
2- Go to Project -> Properties -> Java Compiler
3- Check the option for 'Enable project specific settings'
4- Set the 'Compiler compliance level' to '1.6'
NOTE: If already set to 1.6 then change it to 1.5.
5- Press the 'Apply' button.
There are issues with the IDE and at times it just doesn't pick up the default selected compiler compliance level. Therefore you have to toggle it and press the apply button for the changes to take effect.
Having read the responses to date, I can see that there is some confusion as to what is happening where Eclipse is involved.
I had the same syntax error, checked workspace Java compliance (Window > Preferences > Java > Compiler) and was surprised to see a complier compliance level of 1.6. However, I noticed the link Configure Project Specific Settings at the top of this preference page. The link takes you to the project's own settings.
You can navigate there from the main menu, too. In this case Project > Properties > Java Compiler. There is a check box labelled Enable Project Settings and in my case this was checked and the setting was 1.4, though I do not remember setting it explicitly. Anyway, you can either let the compliance setting to default to that of the workbench or change the project setting to 1.5 or higher.
This should fix the syntax error.
I suspect you've got your source level set to lower than 1.5. It should be fine in Java 6 in general.
How are you compiling? If it's with Eclipse, what do your project/workspace settings say under Compiler / JDK Compliance Level?
If you're using javac, run
javac -version
to check what version you're really using.
Are you sure you are compiling with Java 1.6 not 1.4 (or older)?
What compiler are you using?
#Deprecated not #Deprecate
If you are using Eclipse, make sure the settings for the Java Compiler are set to 1.6 compliance.
This can occur even if java 1.6 is used in eclipse. Click the project and then right click it. Go to properties and in Java compiler section first check enable project specific then manually select 1.6 version even if it is already there by default. This fixed my problem.