polish all java and C# ModelBuilder samples

ortools/linear_solver/samples/AssignmentMb.java

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+// Copyright 2010-2022 Google LLC
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// 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.
+
+// [START program]
+package com.google.ortools.linearsolver.samples;
+// [START import]
+import com.google.ortools.Loader;
+import com.google.ortools.modelbuilder.LinearConstraint;
+import com.google.ortools.modelbuilder.LinearExpr;
+import com.google.ortools.modelbuilder.LinearExprBuilder;
+import com.google.ortools.modelbuilder.ModelBuilder;
+import com.google.ortools.modelbuilder.ModelSolver;
+import com.google.ortools.modelbuilder.SolveStatus;
+import com.google.ortools.modelbuilder.Variable;
+// [END import]
+
+/** MIP example that solves an assignment problem. */
+public class AssignmentMb {
+  public static void main(String[] args) {
+    Loader.loadNativeLibraries();
+    // Data
+    // [START data_model]
+    double[][] costs = {
+        {90, 80, 75, 70},
+        {35, 85, 55, 65},
+        {125, 95, 90, 95},
+        {45, 110, 95, 115},
+        {50, 100, 90, 100},
+    };
+    int numWorkers = costs.length;
+    int numTasks = costs[0].length;
+    // [END data_model]
+
+    // [START model]
+    ModelBuilder model = new ModelBuilder();
+    // [END model]
+
+    // Variables
+    // [START variables]
+    // x[i][j] is an array of 0-1 variables, which will be 1
+    // if worker i is assigned to task j.
+    Variable[][] x = new Variable[numWorkers][numTasks];
+    for (int i = 0; i < numWorkers; ++i) {
+      for (int j = 0; j < numTasks; ++j) {
+        x[i][j] = model.newBoolVar("");
+      }
+    }
+    // [END variables]
+
+    // Constraints
+    // [START constraints]
+    // Each worker is assigned to at most one task.
+    for (int i = 0; i < numWorkers; ++i) {
+      LinearExprBuilder assignedWork = LinearExpr.newBuilder();
+      for (int j = 0; j < numTasks; ++j) {
+        assignedWork.add(x[i][j]);
+      }
+      model.addLessOrEqual(assignedWork, 1);
+    }
+
+    // Each task is assigned to exactly one worker.
+    for (int j = 0; j < numTasks; ++j) {
+      LinearExprBuilder assignedWorker = LinearExpr.newBuilder();
+      for (int i = 0; i < numWorkers; ++i) {
+        assignedWorker.add(x[i][j]);
+      }
+      model.addEquality(assignedWorker, 1);
+    }
+    // [END constraints]
+
+    // Objective
+    // [START objective]
+    LinearExprBuilder objective = LinearExpr.newBuilder();
+    for (int i = 0; i < numWorkers; ++i) {
+      for (int j = 0; j < numTasks; ++j) {
+        objective.addTerm(x[i][j], costs[i][j]);
+      }
+    }
+    model.minimize(objective);
+    // [END objective]
+
+    // [START solver]
+    // Create the solver with the SCIP backend and check it is supported.
+    ModelSolver solver = new ModelSolver("scip");
+    if (!solver.solverIsSupported()) return;
+    // [END solver]
+
+    // [START solve]
+    final SolveStatus resultStatus = solver.solve(model);
+    // [END solve]
+
+    // Print solution.
+    // [START print_solution]
+    // Check that the problem has a feasible solution.
+    if (resultStatus == SolveStatus.OPTIMAL || resultStatus == SolveStatus.FEASIBLE) {
+      System.out.println("Total cost: " + solver.getObjectiveValue() + "\n");
+      for (int i = 0; i < numWorkers; ++i) {
+        for (int j = 0; j < numTasks; ++j) {
+          // Test if x[i][j] is 0 or 1 (with tolerance for floating point
+          // arithmetic).
+          if (solver.getValue(x[i][j]) > 0.9) {
+            System.out.println(
+                "Worker " + i + " assigned to task " + j + ".  Cost = " + costs[i][j]);
+          }
+        }
+      }
+    } else {
+      System.err.println("No solution found.");
+    }
+    // [END print_solution]
+  }
+
+  private AssignmentMb() {}
+}
+// [END program]