updated javac version to 1.8 to fix the warning
updated javac version to 1.8 to fix the warning

ProjectSidewalk/SidewalkWebpage,ProjectSidewalk/SidewalkWebpage,ProjectSidewalk/SidewalkWebpage,ProjectSidewalk/SidewalkWebpage,ProjectSidewalk/SidewalkWebpage,ProjectSidewalk/SidewalkWebpage