Add solution of JewelsAndStones task

Author: andrei-punko

src/main/java/by/andd3dfx/string/JewelsAndStones.java

@@ -0,0 +1,46 @@
+package by.andd3dfx.string;
+
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/**
+ * <pre>
+ * <a href="https://leetcode.com/problems/jewels-and-stones/description/">Task description</a>
+ *
+ * You're given strings jewels representing the types of stones that are jewels, and stones
+ * representing the stones you have. Each character in stones is a type of stone you have.
+ * You want to know how many of the stones you have are also jewels.
+ * Letters are case sensitive, so "a" is considered a different type of stone from "A".
+ *
+ * Example 1:
+ * Input: jewels = "aA", stones = "aAAbbbb"
+ * Output: 3
+ *
+ * Example 2:
+ * Input: jewels = "z", stones = "ZZ"
+ * Output: 0
+ * </pre>
+ */
+public class JewelsAndStones {
+
+    public static int numJewelsInStones(String jewels, String stones) {
+        var count = 0;
+        for (var ch : stones.toCharArray()) {
+            if (jewels.indexOf(ch) != -1) {
+                count++;
+            }
+        }
+        return count;
+    }
+
+    public static int numJewelsInStones2(String jewels, String stones) {
+        Set<Character> jewelsSet = jewels.chars()
+            .mapToObj(jewel -> (char) jewel)
+            .collect(Collectors.toSet());
+
+        return (int) stones.chars()
+            .mapToObj(stone -> (char) stone)
+            .filter(jewelsSet::contains)
+            .count();
+    }
+}

src/test/java/by/andd3dfx/string/JewelsAndStonesTest.java

@@ -0,0 +1,22 @@
+package by.andd3dfx.string;
+
+import static by.andd3dfx.string.JewelsAndStones.numJewelsInStones;
+import static by.andd3dfx.string.JewelsAndStones.numJewelsInStones2;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.Test;
+
+public class JewelsAndStonesTest {
+
+    @Test
+    public void testNumJewelsInStones() {
+        assertThat(numJewelsInStones("aA", "aAAbbbb")).isEqualTo(3);
+        assertThat(numJewelsInStones("z", "ZZ")).isEqualTo(0);
+    }
+
+    @Test
+    public void testNumJewelsInStones2() {
+        assertThat(numJewelsInStones2("aA", "aAAbbbb")).isEqualTo(3);
+        assertThat(numJewelsInStones2("z", "ZZ")).isEqualTo(0);
+    }
+}