java: Fix package in examples/contrib and examples/java

examples/java/LinearAssignmentAPI.java

@@ -10,6 +10,7 @@
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
+package com.google.ortools.examples;
 
 import com.google.ortools.graph.LinearSumAssignment;