Add Either#from

2bllw8 · Jul 3, 2022 · 8b6210e · 8b6210e
1 parent 5231010
commit 8b6210e
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diff --git a/lib/src/main/java/exe/bbllw8/either/Either.java b/lib/src/main/java/exe/bbllw8/either/Either.java
@@ -7,6 +7,7 @@
 import java.util.Optional;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.function.Supplier;
 import java.util.stream.Stream;
 
 /**
@@ -19,6 +20,8 @@
  * <ul>
  *     <li>{@link Left}: instance with a left value</li>
  *     <li>{@link Right}: instance with a right value</li>
+ *     <li>{@link Either#from(boolean, Supplier, Supplier)}: instance from the evaluation
+ *         of a supplied boolean value</li>
  * </ul>
  * <p>
  * This class is not serializable.
@@ -37,6 +40,7 @@ public abstract class Either<A, B> {
      * <ul>
      *     <li>{@link Left}</li>
      *     <li>{@link Right}</li>
+     *     <li>{@link Either#from(boolean, Supplier, Supplier)}</li>
      * </ul>
      *
      * @hidden
@@ -174,6 +178,19 @@ public abstract class Either<A, B> {
      */
     public abstract Optional<B> toOptional();
 
+    /**
+     * @return If the <code>conditional</code> is <code>true</code> returns a {@link Right} holding
+     * the value supplied by <code>ifTrue</code>, otherwise a {@link Left} holding the value
+     * supplied by the <code>ifFalse</code>
+     * @since 3.4.0
+     */
+    public static <A, B> Either<A, B> from(boolean conditional, Supplier<B> ifTrue,
+            Supplier<A> ifFalse) {
+        return conditional
+                ? new Right<>(ifTrue.get())
+                : new Left<>(ifFalse.get());
+    }
+
     /**
      * @return Returns the right value if the given argument is {@link Right} or its value if it is
      * {@link Left}.

diff --git a/lib/src/test/java/exe/bbllw8/either/EitherTest.java b/lib/src/test/java/exe/bbllw8/either/EitherTest.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2022 2bllw8
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package exe.bbllw8.either;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public final class EitherTest {
+
+    @Test
+    public void from() {
+        Assert.assertTrue("Should return a Right if the conditional supplies a true value",
+                Either.from(true, () -> 0, () -> 0) instanceof Right);
+        Assert.assertTrue("Should return a Left if the conditional supplies a false value",
+                Either.from(false, () -> 0, () -> 0) instanceof Left);
+        Assert.assertEquals("Should return the value supplied by the ifTrue parameter",
+                new Right<>(1),
+                Either.from(true, () -> 1, () -> 0));
+        Assert.assertEquals("Should return the value supplied by the ifFalse parameter",
+                new Left<>(0),
+                Either.from(false, () -> 1, () -> 0));
+    }
+}