contrib: cleanup few java examples

examples/contrib/DietMIP.java

@@ -27,7 +27,12 @@ import com.google.ortools.linearsolver.MPVariable;
 
 public class DietMIP {
   private static void solve(String solverType) {
+    System.out.println("---- DietMIP with " + solverType);
+
     MPSolver solver = MPSolver.createSolver(solverType);
+    if (solver == null)
+      return;
+
     double infinity = MPSolver.infinity();
 
     int n = 4; // variables number
@@ -77,6 +82,7 @@ public class DietMIP {
 
   public static void main(String[] args) throws Exception {
     Loader.loadNativeLibraries();
+    solve("SCIP");
     solve("CBC");
   }
 }

examples/contrib/StiglerMIP.java

@@ -200,9 +200,12 @@ public class StiglerMIP {
       }
     }
 
-    solver.solve();
+    final MPSolver.ResultStatus resultStatus = solver.solve();
 
     /** printing */
+    if (resultStatus != MPSolver.ResultStatus.OPTIMAL) {
+      System.err.println("The problem does not have an optimal solution!");
+    }
     DecimalFormat df = new DecimalFormat("#.##");
     df.setRoundingMode(RoundingMode.CEILING);