diff --git a/src/main/java/com/treasuredata/client/TDHttpClient.java b/src/main/java/com/treasuredata/client/TDHttpClient.java
index 07fdb62a..95befd0e 100644
--- a/src/main/java/com/treasuredata/client/TDHttpClient.java
+++ b/src/main/java/com/treasuredata/client/TDHttpClient.java
@@ -210,7 +210,7 @@ public Request prepareRequest(TDApiRequest apiRequest, Optional<String> apiKeyCa
                 : String.format("%s://%s%s%s", config.useSSL ? "https" : "http", config.endpoint, portStr, apiRequest.getPath());
 
         if (!apiRequest.getQueryParams().isEmpty()) {
-            List<String> queryParamList = new ArrayList<String>(apiRequest.getQueryParams().size());
+            List<String> queryParamList = new ArrayList<>(apiRequest.getQueryParams().size());
             for (Map.Entry<String, String> queryParam : apiRequest.getQueryParams().entrySet()) {
                 queryParamList.add(String.format("%s=%s", urlEncode(queryParam.getKey()), urlEncode(queryParam.getValue())));
             }
diff --git a/src/main/java/com/treasuredata/client/model/TDColumn.java b/src/main/java/com/treasuredata/client/model/TDColumn.java
index 5c47770a..95a7940f 100644
--- a/src/main/java/com/treasuredata/client/model/TDColumn.java
+++ b/src/main/java/com/treasuredata/client/model/TDColumn.java
@@ -108,7 +108,7 @@ public static List<TDColumn> parseTuple(String jsonStr)
         try {
             String unescaped = jsonStr.replaceAll("\\\"", "\"");
             JSONArray arr = castToArray(new JSONParser().parse(unescaped));
-            List<TDColumn> columnList = new ArrayList<TDColumn>(arr.size());
+            List<TDColumn> columnList = new ArrayList<>(arr.size());
             for (Object e : arr) {
                 JSONArray columnNameAndType = castToArray(e);
                 String[] s = new String[columnNameAndType.size()];
@@ -121,7 +121,7 @@ public static List<TDColumn> parseTuple(String jsonStr)
         }
         catch (ParseException e) {
             LoggerFactory.getLogger(TDColumn.class).error("Failed to parse json string", e);
-            return new ArrayList<TDColumn>(0);
+            return new ArrayList<>(0);
         }
     }
 
diff --git a/src/test/java/com/treasuredata/client/TestTDClientConfig.java b/src/test/java/com/treasuredata/client/TestTDClientConfig.java
index 0808d96d..95bd43b8 100644
--- a/src/test/java/com/treasuredata/client/TestTDClientConfig.java
+++ b/src/test/java/com/treasuredata/client/TestTDClientConfig.java
@@ -68,7 +68,7 @@ public class TestTDClientConfig
     static ImmutableMap<TDClientConfig.Type, Object> m;
 
     static {
-        ImmutableMap.Builder p = ImmutableMap.<TDClientConfig.Type, Object>builder();
+        ImmutableMap.Builder<TDClientConfig.Type, Object> p = ImmutableMap.builder();
         p.put(API_ENDPOINT, "api2.treasuredata.com");
         p.put(API_PORT, 8981);
         p.put(USESSL, true);
@@ -83,7 +83,7 @@ public class TestTDClientConfig
         p.put(PASSOWRD, "yyyy");
         m = p.build();
 
-        assertTrue(new HashSet(TDClientConfig.knownProperties()).containsAll(m.keySet()));
+        assertTrue(new HashSet<>(TDClientConfig.knownProperties()).containsAll(m.keySet()));
     }
 
     private void validate(TDClientConfig config)
@@ -136,7 +136,7 @@ public void testConfigParam()
     @Test
     public void testProxyParam()
     {
-        Map<TDClientConfig.Type, Object> m = new HashMap<TDClientConfig.Type, Object>();
+        Map<TDClientConfig.Type, Object> m = new HashMap<>();
         m.put(PROXY_HOST, "localhost1");
         m.put(PROXY_PORT, 8982);
         m.put(PROXY_USER, "pp");