Build passes even with import can not resolve

Hi,

I have imported an Java project in intellij. In the editor, it shows red lines suggesting "Can not resolve symbol 'ArrayList'", but the build passes.


I have done import like below which shows red:

import java.util.ArrayList;
import java.util.Arrays;

and have used as

private ArrayList<String> filePaths = new ArrayList<String>();
private String projectPath;


Could you please suggest if this is a real error and how can we get rid of this?