Merge pull request #15908 from sk1418/string-in-mirror

[string-in-mirror] string - mirror reflection

core-java-modules/core-java-string-algorithms-4/src/test/java/com/baeldung/string/chkstringinmirror/CheckStringEqualsMirrorReflectionUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.string.chkstringinmirror;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Test;
+
+public class CheckStringEqualsMirrorReflectionUnitTest {
+
+    private final static Set<Character> SYMMETRIC_LETTERS = Set.of('A', 'H', 'I', 'M', 'O', 'T', 'U', 'V', 'W', 'X', 'Y');
+
+    @Test
+    void whenCallingIsReflectionEqual_thenGetExpectedResults() {
+        assertFalse(isMirrorImageEqual("LOL"));
+        assertFalse(isMirrorImageEqual("AXY"));
+        assertFalse(isMirrorImageEqual("HUHU"));
+
+        assertTrue(isMirrorImageEqual(""));
+        assertTrue(isMirrorImageEqual("AAA"));
+        assertTrue(isMirrorImageEqual("HUH"));
+        assertTrue(isMirrorImageEqual("HIMMIH"));
+        assertTrue(isMirrorImageEqual("HIMIH"));
+    }
+
+
+    public boolean isMirrorImageEqual(String input) {
+        return containsOnlySymmetricLetters(input) && isPalindrome(input);
+    }
+
+    private boolean containsOnlySymmetricLetters(String input) {
+        Set<Character> characterSet = input.chars()
+            .mapToObj(c -> (char) c)
+            .collect(Collectors.toSet());
+        characterSet.removeAll(SYMMETRIC_LETTERS);
+        return characterSet.isEmpty();
+    }
+
+    private boolean isPalindrome(String input) {
+        String reversed = new StringBuilder(input).reverse()
+            .toString();
+        return input.equals(reversed);
+    }
+
+}