BAEL-6818 Add examples for checking if a value exists in a JSON array

json-modules/json-arrays/src/test/java/com.baeldung.checkforkey/CheckForKeyUnitTest.java

@@ -0,0 +1,45 @@
+package com.baeldung.checkforkey;
+
+import java.util.Objects;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import org.junit.jupiter.api.Test;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.google.gson.Gson;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+
+public class CheckForKeyUnitTest {
+
+    private final String exampleJson = "[{\"colour\":\"red\"},{\"colour\":\"blue\"},{\"colour\":\"green\"}]";
+
+    @Test
+    public void givenJsonArray_whenUsingJackson_thenDetectKeyInArray() throws JsonProcessingException {
+        ObjectMapper objectMapper = new ObjectMapper();
+        JsonNode tree = objectMapper.readTree(exampleJson);
+
+        Stream<JsonNode> s = StreamSupport.stream(tree.spliterator(), false);
+        boolean result = s.map(entry -> entry.get("colour"))
+          .filter(Objects::nonNull)
+          .anyMatch(colour -> "green".equals(colour.asText()));
+        assert (result);
+    }
+
+    @Test
+    public void givenJsonArray_whenUsingGson_thenDetectKeyInArray() {
+        Gson gson = new Gson();
+        JsonArray parsed = gson.fromJson(exampleJson, JsonArray.class);
+
+        Stream<JsonElement> s = StreamSupport.stream(parsed.spliterator(), false);
+        boolean result = s.map(entry -> entry.getAsJsonObject()
+          .get("colour"))
+          .filter(Objects::nonNull)
+          .anyMatch(colour -> "green".equals(colour.getAsString()));
+        assert (result);
+    }
+
+}