Use javac.target=1.6 for Java 11

Author: vlsi

.travis.yml

@@ -2,6 +2,23 @@ sudo: false
 language: java
 dist: trusty
 
-jdk:
-  - oraclejdk8
-  - oraclejdk11
+before_cache:
+  # No sense in caching current build artifacts
+  rm -rf $HOME/.m2/repository/com/github/vlsi
+
+install:
+  - mvn -Djavac.target=$TRGT install -DskipTests=true -Dmaven.javadoc.skip=true -B -V
+
+script:
+  - mvn -Djavac.target=$TRGT test -B
+
+matrix:
+  include:
+  - jdk: oraclejdk8
+    env:
+    - JDK=8
+    - TRGT=1.5
+  - jdk: oraclejdk11
+    env:
+    - JDK=11
+    - TRGT=1.6

pom.xml

@@ -14,6 +14,7 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <javac.target>1.5</javac.target>
     </properties>
 
     <name>Compact HashMap parent</name>
@@ -109,8 +110,8 @@
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-compiler-plugin</artifactId>
                     <configuration>
-                        <source>1.5</source>
-                        <target>1.5</target>
+                        <source>${javac.target}</source>
+                        <target>${javac.target}</target>
                     </configuration>
                 </plugin>
                 <plugin>