[Java] Update travis build.

Author: mjpt777

.travis.yml

@@ -1,10 +1,20 @@
 
 sudo: false
 
+before_cache:
+- rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
+- rm -fr $HOME/.gradle/caches/*/plugin-resolution/
+
+cache:
+  directories:
+  - $HOME/.gradle/caches/
+  - $HOME/.gradle/wrapper/
+
 matrix:
   include:
 
     # clang-4
+    - language: cpp
     - env: COMPILER=clang++-4.0
       compiler: clang
       os: linux
@@ -19,6 +29,7 @@ matrix:
             - llvm-toolchain-trusty-4.0
 
     # clang-5
+    - language: cpp
     - env: COMPILER=clang++-5.0
       compiler: clang
       os: linux
@@ -33,6 +44,7 @@ matrix:
             - llvm-toolchain-trusty-5.0
 
     # clang-6
+    - language: cpp
     - env: COMPILER=clang++-6.0
       compiler: clang
       os: linux
@@ -47,6 +59,7 @@ matrix:
             - llvm-toolchain-trusty-6.0
 
     # gcc-5
+    - language: cpp
     - env: COMPILER=g++-5
       compiler: gcc
       os: linux
@@ -59,6 +72,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     # gcc-6
+    - language: cpp
     - env: COMPILER=g++-6
       compiler: gcc
       os: linux
@@ -71,6 +85,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     # gcc-7
+    - language: cpp
     - env: COMPILER=g++-7
       compiler: gcc
       os: linux
@@ -83,6 +98,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     # gcc-8
+    - language: cpp
     - env: COMPILER=g++-8
       compiler: gcc
       os: linux
@@ -98,14 +114,5 @@ before_script:
   - export CXX=$COMPILER
   - ./gradlew
 
-before_cache:
-  - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
-  - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
-
-cache:
-  directories:
-    - $HOME/.gradle/caches/
-    - $HOME/.gradle/wrapper/
-
 script:
   - ./cppbuild/cppbuild