Add LeftProjection#contains

2bllw8 · Jun 28, 2022 · a0e0bfd · a0e0bfd
1 parent dd54999
commit a0e0bfd
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Showing 4 changed files with 31 additions and 0 deletions.
diff --git a/lib/src/main/java/exe/bbllw8/either/Left.java b/lib/src/main/java/exe/bbllw8/either/Left.java
@@ -162,6 +162,11 @@ private LeftToLeftProjection(A value) {
             this.value = value;
         }
 
+        @Override
+        public boolean contains(B elem) {
+            return Objects.equals(value, elem);
+        }
+
         @Override
         public boolean exists(Function<A, Boolean> predicate) {
             return predicate.apply(value);

diff --git a/lib/src/main/java/exe/bbllw8/either/LeftProjection.java b/lib/src/main/java/exe/bbllw8/either/LeftProjection.java
@@ -25,6 +25,17 @@ public abstract class LeftProjection<A, B> {
     /* package */ LeftProjection() {
     }
 
+    /**
+     * Returns true if this holds a {@link Left} value and its value is equal to elem (as determined
+     * by {@link Object#equals(Object)}), returns false otherwise.
+     *
+     * @param elem The element to test.
+     * @return <code>true</code> if this holds a {@link Left} value that is equal to
+     * <code>elem</code>
+     * @since 3.4.0
+     */
+    public abstract boolean contains(B elem);
+
     /**
      * @return Returns false if {@link Right} or returns the result of the application of the given
      * function to the {@link Left} value.

diff --git a/lib/src/main/java/exe/bbllw8/either/Right.java b/lib/src/main/java/exe/bbllw8/either/Right.java
@@ -164,6 +164,11 @@ private RightToLeftProjection(B value) {
             this.value = value;
         }
 
+        @Override
+        public boolean contains(B elem) {
+            return false;
+        }
+
         @Override
         public boolean exists(Function<A, Boolean> predicate) {
             return false;

diff --git a/lib/src/test/java/exe/bbllw8/either/LeftProjectionTest.java b/lib/src/test/java/exe/bbllw8/either/LeftProjectionTest.java
@@ -11,6 +11,16 @@
 
 public class LeftProjectionTest {
 
+    @Test
+    public void contains() {
+        Assert.assertTrue("Contains should return true if the values are equal",
+                new Left<>(12).left().contains(12));
+        Assert.assertFalse("Contains should return false if the values are not equal",
+                new Left<>(7).left().contains(10));
+        Assert.assertFalse("Exists should return false if the projection is from a Right",
+                new Right<Integer, Integer>(12).left().contains(12));
+    }
+
     @Test
     public void exists() {
         Assert.assertTrue("Exists should return true if the predicate is satisfied",