Experiment with ad-hoc methods

Author: Nicolai Parlog

src/main/java/org/codefx/demo/java10/lang/var/AdHocMethods.java

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+package org.codefx.demo.java10.lang.var;
+
+import java.math.BigDecimal;
+
+public class AdHocMethods {
+
+	/*
+	 * DOWNSIDES
+	 *
+	 *  - verbose
+	 *  - combination of non-trivial language features (anonymous types & type inference)
+	 *  - falls apart when extracting methods
+	 *
+	 * ALTERNATIVES
+	 *
+	 *  - extension type collecting all needed methods
+	 *  - utility methods
+	 */
+
+	public void report(Megacorp megacorp) {
+		var corp = new SimpleMegacorp(megacorp) {
+			final BigDecimal SUCCESS_BOUNDARY = new BigDecimal("500000000");
+
+			boolean isSuccessful() {
+				return earnings().compareTo(SUCCESS_BOUNDARY) > 0;
+			}
+
+			boolean isEvil() {
+				return true;
+			}
+		};
+		System.out.printf(
+				"Corporation %s is %s and %s.\n",
+				corp.name(),
+				corp.isSuccessful() ? "successful" : "a failure",
+				corp.isEvil() ? "evil" : "a failure"
+		);
+	}
+
+	// important domain concept, used throughout the system
+	interface Megacorp {
+
+		String name();
+
+		BigDecimal earnings();
+
+		BigDecimal taxes();
+
+	}
+
+	// some implementation
+	class SimpleMegacorp implements Megacorp {
+
+		private final String name;
+		private final BigDecimal earnings;
+		private final BigDecimal taxes;
+
+		SimpleMegacorp(String name, BigDecimal earnings, BigDecimal taxes) {
+			this.name = name;
+			this.earnings = earnings;
+			this.taxes = taxes;
+		}
+
+		public SimpleMegacorp(Megacorp megacorp) {
+			this(megacorp.name(), megacorp.earnings(), megacorp.taxes());
+		}
+
+		@Override
+		public String name() {
+			return name;
+		}
+
+		@Override
+		public BigDecimal earnings() {
+			return earnings;
+		}
+
+		@Override
+		public BigDecimal taxes() {
+			return taxes;
+		}
+
+	}
+
+}