Java. Warning - Build path specifies execution environment J2SE-1.4

Question

I creat a Maven Project in the Eclipse Helios. It works fine for a day, but one moment emerge this warning

Build path specifies execution environment J2SE-1.4. There are no JREs installed in the workspace that are strictly compatible with this environment.

Since this message project no more compiling and debugging. Does anyone have solution for this problem?

Answer 1

In eclipse preferences, go to Java->Installed JREs->Execution Environment and set up a JRE Execution Environment for J2SE-1.4

Answer 2

Did you setup your project to be compiled with 1.4 compliance? If so, do what krock said. Or to be more exact you need to select the J2SE-1.4 execution environment and check one of the installed JRE that you want to use in 1.4 compliance mode; most likely you'll have a 1.6 JRE installed, just check that one. Or install a 1.4 JRE if you have a setup kit, and use that one.

Otherwise go to your Eclipse preferences, Java -> Compiler and check if the compliance is set to 1.4. If it is change it back to 1.6. If it's not go to the project properties, and check if it has project specific settings. Go to Java Compiler, and uncheck that if you want to use the general eclipse preferences. Or set the project specific settings to 1.6, so that it's always 1.6 regardless of eclipse preferences.

Answer 3

Whether you're using the maven eclipse plugin or m2eclipse, Eclipse's project configuration is derived from the POM, so you need to configure the maven compiler plugin for 1.6 (it defaults to 1.4):

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>          
        <configuration>
            <source>1.6</source>
            <target>1.6</target>
        </configuration>
    </plugin>
</plugins>