Red × on the project maven java resource, but the file is error-free.

Copyright: Attribution, allow others to create paper-based, and must distribute paper (based on the original license agreement with the same license Creative Commons )

1, add the following plug-in pom.xml

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.0</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
  </build>

That the use of jdk1.8 not use the default compiler.
2, no change pom.xml file Maven → update project, eclipse the problems will prompt function, will be displayed on the Java Resouse project directory, it will display a red cross ×.