Why so red? IntelliJ seems to think every declaration/method cannot be found/resolved

Question

I just installed and re-installed IntelliJ. Every Java file is coming up RED. I checked the JDK; it is at 1.6.##. The maven clean install build worked just fine

Answer 1

My problem solved by changing jdk to default , like this. Open Jdk was installed but don't know why intellij set configuration to java-8-openjdk-amd64. This was the problem.I have changed to default-java and no more red error.