diff --git a/logstash-core/src/test/java/org/logstash/AccessorsTest.java b/logstash-core/src/test/java/org/logstash/AccessorsTest.java
index 0008ed3f7..c517da040 100644
--- a/logstash-core/src/test/java/org/logstash/AccessorsTest.java
+++ b/logstash-core/src/test/java/org/logstash/AccessorsTest.java
@@ -67,7 +67,7 @@ public class AccessorsTest {
     @Test
     public void testDeepListGet() throws Exception {
         Map<Serializable, Object>  data = new HashMap<>();
-        List inner = new ArrayList();
+        List<String> inner = new ArrayList<>();
         data.put("foo", inner);
         inner.add("bar");
         String reference = "[foo][0]";
@@ -79,7 +79,7 @@ public class AccessorsTest {
     @Test
     public void testAbsentDeepListGet() throws Exception {
         Map<Serializable, Object>  data = new HashMap<>();
-        List inner = new ArrayList();
+        List<String> inner = new ArrayList<>();
         data.put("foo", inner);
         inner.add("bar");
         String reference = "[foo][1]";
@@ -94,7 +94,7 @@ public class AccessorsTest {
     @Test
     public void testInvalidIdList() throws Exception {
         final ConvertedMap data = new ConvertedMap(1);
-        List inner = new ConvertedList(2);
+        List<Object> inner = new ConvertedList(2);
         data.put("map1", inner);
         inner.add("obj1");
         inner.add("obj2");
@@ -137,7 +137,7 @@ public class AccessorsTest {
     @Test
     public void testDel() throws Exception {
         final ConvertedMap data = new ConvertedMap(1);
-        List inner = new ConvertedList(1);
+        List<Object> inner = new ConvertedList(1);
         data.put("foo", inner);
         inner.add("bar");
         data.put("bar", "baz");
diff --git a/logstash-core/src/test/java/org/logstash/KeyNodeTest.java b/logstash-core/src/test/java/org/logstash/KeyNodeTest.java
index ea5b69c89..df9a0243c 100644
--- a/logstash-core/src/test/java/org/logstash/KeyNodeTest.java
+++ b/logstash-core/src/test/java/org/logstash/KeyNodeTest.java
@@ -12,7 +12,7 @@ public class KeyNodeTest {
 
     @Test
     public void testNoElementJoin() throws IOException {
-        assertEquals("", KeyNode.join(new ArrayList(), ","));
+        assertEquals("", KeyNode.join(new ArrayList<>(), ","));
     }
 
     @Test
diff --git a/logstash-core/src/test/java/org/logstash/RubyfierTest.java b/logstash-core/src/test/java/org/logstash/RubyfierTest.java
index df14a7072..a26dbc7fd 100644
--- a/logstash-core/src/test/java/org/logstash/RubyfierTest.java
+++ b/logstash-core/src/test/java/org/logstash/RubyfierTest.java
@@ -31,10 +31,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepMapWithString()
-            throws Exception
-    {
-        Map data = new HashMap();
+    public void testDeepMapWithString() throws Exception {
+        Map<String, String> data = new HashMap<>();
         data.put("foo", "bar");
         RubyHash rubyHash = ((RubyHash) Rubyfier.deep(ruby, data));
 
@@ -50,10 +48,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepListWithString()
-            throws Exception
-    {
-        List data = new ArrayList();
+    public void testDeepListWithString() throws Exception {
+        List<String> data = new ArrayList<>();
         data.add("foo");
 
         RubyArray rubyArray = ((RubyArray)Rubyfier.deep(ruby, data));
@@ -71,10 +67,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepMapWithInteger()
-            throws Exception
-    {
-        Map data = new HashMap();
+    public void testDeepMapWithInteger() throws Exception {
+        Map<String, Integer> data = new HashMap<>();
         data.put("foo", 1);
         RubyHash rubyHash = ((RubyHash)Rubyfier.deep(ruby, data));
 
@@ -90,10 +84,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepListWithInteger()
-            throws Exception
-    {
-        List data = new ArrayList();
+    public void testDeepListWithInteger() throws Exception {
+        List<Integer> data = new ArrayList<>();
         data.add(1);
 
         RubyArray rubyArray = ((RubyArray)Rubyfier.deep(ruby, data));
@@ -111,10 +103,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepMapWithFloat()
-            throws Exception
-    {
-        Map data = new HashMap();
+    public void testDeepMapWithFloat() throws Exception {
+        Map<String, Float> data = new HashMap<>();
         data.put("foo", 1.0F);
         RubyHash rubyHash = ((RubyHash)Rubyfier.deep(ruby, data));
 
@@ -130,10 +120,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepListWithFloat()
-            throws Exception
-    {
-        List data = new ArrayList();
+    public void testDeepListWithFloat() throws Exception {
+        List<Float> data = new ArrayList<>();
         data.add(1.0F);
 
         RubyArray rubyArray = ((RubyArray)Rubyfier.deep(ruby, data));
@@ -151,10 +139,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepMapWithDouble()
-            throws Exception
-    {
-        Map data = new HashMap();
+    public void testDeepMapWithDouble() throws Exception {
+        Map<String, Double> data = new HashMap<>();
         data.put("foo", 1.0D);
         RubyHash rubyHash = ((RubyHash)Rubyfier.deep(ruby, data));
 
@@ -170,10 +156,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepListWithDouble()
-            throws Exception
-    {
-        List data = new ArrayList();
+    public void testDeepListWithDouble() throws Exception {
+        List<Double> data = new ArrayList<>();
         data.add(1.0D);
 
         RubyArray rubyArray = ((RubyArray)Rubyfier.deep(ruby, data));
@@ -191,10 +175,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepMapWithBigDecimal()
-            throws Exception
-    {
-        Map data = new HashMap();
+    public void testDeepMapWithBigDecimal() throws Exception {
+        Map<String, BigDecimal> data = new HashMap<>();
         data.put("foo", new BigDecimal(1));
 
         RubyHash rubyHash = ((RubyHash)Rubyfier.deep(ruby, data));
@@ -211,10 +193,8 @@ public class RubyfierTest extends TestBase {
     }
 
     @Test
-    public void testDeepListWithBigDecimal()
-            throws Exception
-    {
-        List data = new ArrayList();
+    public void testDeepListWithBigDecimal() throws Exception {
+        List<BigDecimal> data = new ArrayList<>();
         data.add(new BigDecimal(1));
 
         RubyArray rubyArray = ((RubyArray)Rubyfier.deep(ruby, data));
diff --git a/logstash-core/src/test/java/org/logstash/StringInterpolationTest.java b/logstash-core/src/test/java/org/logstash/StringInterpolationTest.java
index 3753b5806..1371a4952 100644
--- a/logstash-core/src/test/java/org/logstash/StringInterpolationTest.java
+++ b/logstash-core/src/test/java/org/logstash/StringInterpolationTest.java
@@ -93,7 +93,7 @@ public class StringInterpolationTest {
 
     @Test
     public void TestValueIsArray() throws IOException {
-        ArrayList l = new ArrayList();
+        ArrayList<String> l = new ArrayList<>();
         l.add("Hello");
         l.add("world");
 
@@ -113,8 +113,8 @@ public class StringInterpolationTest {
     }
 
     public Event getTestEvent() {
-        Map data = new HashMap();
-        Map inner = new HashMap();
+        Map<String, Object> data = new HashMap<>();
+        Map<String, String> inner = new HashMap<>();
 
         inner.put("k1", "v");
 
diff --git a/logstash-core/src/test/java/org/logstash/common/io/RecordIOReaderTest.java b/logstash-core/src/test/java/org/logstash/common/io/RecordIOReaderTest.java
index 26520e110..58d8aba68 100644
--- a/logstash-core/src/test/java/org/logstash/common/io/RecordIOReaderTest.java
+++ b/logstash-core/src/test/java/org/logstash/common/io/RecordIOReaderTest.java
@@ -131,7 +131,7 @@ public class RecordIOReaderTest {
 
     private void writeSeekAndVerify(final int eventCount, final int expectedSize) throws IOException {
         int blocks = (int)Math.ceil(expectedSize / (double)BLOCK_SIZE);
-        int fillSize = (int) (expectedSize - (blocks * RECORD_HEADER_SIZE));
+        int fillSize = expectedSize - (blocks * RECORD_HEADER_SIZE);
 
         try(RecordIOWriter writer = new RecordIOWriter(file)){
             for (char i = 0; i < eventCount; i++) {
@@ -145,7 +145,7 @@ public class RecordIOReaderTest {
             Function<byte[], Character> toChar = (b) -> (char) ByteBuffer.wrap(b).get(0);
 
             for (char i = 0; i < eventCount; i++) {
-                reader.seekToNextEventPosition(i, toChar, Comparator.comparing(o -> ((Character) o)));
+                reader.seekToNextEventPosition(i, toChar, Comparator.comparing(o -> o));
                 assertThat(toChar.apply(reader.readEvent()), equalTo(i));
             }
         }
diff --git a/logstash-core/src/test/java/org/logstash/instrument/metrics/MetricTypeTest.java b/logstash-core/src/test/java/org/logstash/instrument/metrics/MetricTypeTest.java
index 4e95c74b4..7a7bec6e1 100644
--- a/logstash-core/src/test/java/org/logstash/instrument/metrics/MetricTypeTest.java
+++ b/logstash-core/src/test/java/org/logstash/instrument/metrics/MetricTypeTest.java
@@ -20,7 +20,7 @@ public class MetricTypeTest {
      */
     @Test
     public void ensurePassivity(){
-        Map<MetricType, String>  nameMap = new HashMap(EnumSet.allOf(MetricType.class).size());
+        Map<MetricType, String> nameMap = new HashMap<>(EnumSet.allOf(MetricType.class).size());
         nameMap.put(MetricType.COUNTER_LONG, "counter/long");
         nameMap.put(MetricType.GAUGE_TEXT, "gauge/text");
         nameMap.put(MetricType.GAUGE_BOOLEAN, "gauge/boolean");
diff --git a/logstash-core/src/test/java/org/logstash/stress/Concurrent.java b/logstash-core/src/test/java/org/logstash/stress/Concurrent.java
index 3fc97fbae..49ba5d3bd 100644
--- a/logstash-core/src/test/java/org/logstash/stress/Concurrent.java
+++ b/logstash-core/src/test/java/org/logstash/stress/Concurrent.java
@@ -108,7 +108,7 @@ public class Concurrent {
 
     public static void oneProducersOneMultipleConsumer() throws IOException, InterruptedException {
         final List<StringElement> input = new ArrayList<>();
-        final Collection<StringElement> output = new ConcurrentLinkedQueue();
+        final Collection<StringElement> output = new ConcurrentLinkedQueue<>();
         final int CONSUMERS = 5;
         List<Thread> consumers = new ArrayList<>();