enumの相互参照

EnumExample3.java

import java.util.function.Supplier;

public class EnumExample3 {

	enum A {
		A1(B.B1, () -> B.B1), A2(B.B2, () -> B.B2);

		private B b;
		private Supplier<B> s;

		A(B b, Supplier<B> s) {
			this.b = b;
			this.s = s;
		}

		public B getB() {
			return b;
		}

		public B getB2() {
			return s.get();
		}
	}

	enum B {
		B1(A.A1, () -> A.A1), B2(A.A2, () -> A.A2);

		private A a;
		private Supplier<A> s;

		B(A a, Supplier<A> s) {
			this.a = a;
			this.s = s;
		}

		public A getA() {
			return a;
		}

		public A getA2() {
			return s.get();
		}
	}

	public static void main(String... args) {
		for (A a : A.values()) {
			System.out.printf("%s(%s %s)\n", a, a.getB(), a.getB2());
		}
		for (B b : B.values()) {
			System.out.printf("%s(%s %s)\n", b, b.getA(), b.getA2());
		}
	}
}

実行結果

A1(B1 B1)
A2(B2 B2)
B1(null A1)
B2(null A2)