1.Window-Preferences-Java-Installed JREs
2.右键项目-Properties-Java Compiler
3.右键项目-Properties-MyEclipse-Project Facets
4.pom文件
<plugins>  
    <plugin>  
        <groupId>org.apache.maven.plugins</groupId>  
        <artifactId>maven-compiler-plugin</artifactId>  
        <version>2.3.2</version>  
        <configuration>  
            <source>1.8</source>//改这里  
            <target>1.8</target>//改这里  
        </configuration>  
    </plugin>  
</plugins>