The Coral Island is a novel by R.M. Ballantyne.
Ralph, Jack, and Peterkin are boys stranded on a desert island who must fight pirates and cannibals to survive.
Lord of the Flies alludes to this premise, but Golding found Ballantyne's treatment naive and improbable. He intended Lord of the Flies to be an indirect critique of The Coral Island. Golding keeps the names of two of Ballantyne's characters, Ralph and Jack, to reinforce the contrast.