The /d/ sound is spelled with <d>, and the /j/ sound is <y>, but is also <i> in poniard and occurs in the letter name U and in words beginning <ew>. Since /j/ can only occur at the start of the syllable in RP, all contrasts are initial.
The contrast is between a voiced stop and a voiced semivowel. It is not a problem for learners.
The only interesting pair to emerge was pondered/poniard, rather too archaic to matter.
The mean density value is 0.4%. The list makes 29 semantic distinctions, a loading of 58%.
D ye dam yam dams yams damn yam damns yams dank yank darn yarn darned yarned darning yarning darns yarns date Yate dates Yeats daw yaw daws yaws daw yore dawn yawn dawned yawned dawning yawning dawns yawns day yea days yeas daze yeas dear year dears years debt yet deer year dell yell dells yells den yen dens yens do ewe do's ewes do U do's U's do yew do's yews do you doer ewer doers ewers don yon door yaw doors yaws door yore dot yacht dots yachts dotted yachted dotting yachting dour you're dung young pondered poniard
John Higgins, Shaftesbury, March 2010.