Eclipse error issues caused by different project versions-about projects written in the JDK1.7 environment, running the JDK1.8 environment

My Computer environment configuration is JDK1.7, the friend is JDK1.8, I put her compiled Java file into the eclipse (Luna version) of my Computer, the project appeared a red exclamation mark, of course, the operation is definitely wrong. So I began the journey of settlement, after a meal toss finally toss well. Below, to commemorate my trip to the wrong line.

First step, display error on Import

In the second step, select the error item and do the following.

The third step: Click Finish after the system will automatically import, then select the project and then right click, select Properties.

Fourth step: According to my marked serial number, step by step click, First point 1, then point 2, the last point 3 (the amount. Awkward), click Finish three appears below the interface, the JDK is set.

Cancel the top tick and select 1.7 ok.

Confirm the change! basically finished.

Final and final "" .....

This is how I solve the problem, I do not know if you have any help.

Eclipse error issues caused by different project versions-about projects written in the JDK1.7 environment, running the JDK1.8 environment