Source code:
@Grab(group='org.openscience.cdk', module='cdk-bundle', version='2.9')
import org.openscience.cdk.interfaces.*;
import org.openscience.cdk.*;
IAtom atom1 = new Atom("C")
IAtom atom2 = new Atom("C")
IAtom atom3 = new Atom("C")
IAtom atom4 = new Atom("C")
IAtom atom5 = new Atom("C")
IAtom atom6 = new Atom("C")
IBond bond1 = new Bond(atom1, atom2, IBond.Order.SINGLE)
IBond bond2 = new Bond(atom2, atom3, IBond.Order.DOUBLE)
IBond bond3 = new Bond(atom3, atom4, IBond.Order.SINGLE)
IBond bond4 = new Bond(atom4, atom5, IBond.Order.DOUBLE)
IBond bond5 = new Bond(atom5, atom6, IBond.Order.SINGLE)
IBond bond6 = new Bond(atom6, atom1, IBond.Order.DOUBLE)
bond1.setFlag(CDKConstants.ISAROMATIC, true);
bond2.setFlag(CDKConstants.ISAROMATIC, true);
bond3.setFlag(CDKConstants.ISAROMATIC, true);
bond4.setFlag(CDKConstants.ISAROMATIC, true);
bond5.setFlag(CDKConstants.ISAROMATIC, true);
bond6.setFlag(CDKConstants.ISAROMATIC, true);
Output: