Add ModelBuilder.clone() java API + sample

ortools/linear_solver/samples/BUILD.bazel

@@ -36,6 +36,8 @@ code_sample_cc(name = "stigler_diet")
 
 # Model Builder
 
+code_sample_java(name = "CloneModelMb")
+
 code_sample_java(name = "SimpleLpProgramMb")
 
 code_sample_java(name = "SimpleMipProgramMb")

ortools/linear_solver/samples/CloneModelMb.java

@@ -0,0 +1,101 @@
+// 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.
+
+// Minimal example to call the MIP solver.
+// [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.ModelBuilder;
+import com.google.ortools.modelbuilder.ModelSolver;
+import com.google.ortools.modelbuilder.SolveStatus;
+import com.google.ortools.modelbuilder.Variable;
+// [END import]
+
+/** Minimal Mixed Integer Programming example to showcase cloning a model. */
+public final class CloneModelMb {
+  public static void main(String[] args) {
+    Loader.loadNativeLibraries();
+    // [START model]
+    // Create the linear model.
+    ModelBuilder model = new ModelBuilder();
+    // [END model]
+
+    // [START variables]
+    double infinity = java.lang.Double.POSITIVE_INFINITY;
+    // x and y are integer non-negative variables.
+    Variable x = model.newIntVar(0.0, infinity, "x");
+    Variable y = model.newIntVar(0.0, infinity, "y");
+    // [END variables]
+
+    // [START constraints]
+    // x + 7 * y <= 17.5.
+    LinearConstraint unusedC1 =
+        model.addLessOrEqual(LinearExpr.newBuilder().add(x).addTerm(y, 7), 17.5).withName("c0");
+
+    // x <= 3.5.
+    LinearConstraint c2 = model.addLessOrEqual(x, 3.5).withName("c1");
+    // [END constraints]
+
+    // [START objective]
+    // Maximize x + 10 * y.
+    model.maximize(LinearExpr.newBuilder().add(x).addTerm(y, 10.0));
+    // [END objective]
+
+    // Deep copy
+    System.out.println("Cloning the model");
+    ModelBuilder modelCopy = model.clone();
+    Variable xCopy = modelCopy.varFromIndex(x.getIndex());
+    Variable yCopy = modelCopy.varFromIndex(y.getIndex());
+    Variable zCopy = modelCopy.newBoolVar("z");
+    LinearConstraint c2Copy = modelCopy.constraintFromIndex(c2.getIndex());
+
+    // Add new constraint.
+    LinearConstraint c3Copy = modelCopy.addGreaterOrEqual(xCopy, 1);
+
+    // Modify a constraint.
+    c2Copy.addTerm(zCopy, 2.0);
+
+    System.out.println("Number of constraints in the original model = " + model.numConstraints());
+    System.out.println("Number of constraints in the cloned model = " + modelCopy.numConstraints());
+
+    // [START solve]
+    // Solve with the SCIP MIP solver.
+    ModelSolver solver = new ModelSolver("scip");
+    final SolveStatus status = solver.solve(modelCopy);
+    // [END solve]
+
+    // [START print_solution]
+    if (status == SolveStatus.OPTIMAL) {
+      System.out.println("Solution:");
+      System.out.println("Objective value = " + solver.getObjectiveValue());
+      System.out.println("x = " + solver.getValue(xCopy));
+      System.out.println("y = " + solver.getValue(yCopy));
+      System.out.println("z = " + solver.getValue(zCopy));
+    } else {
+      System.err.println("The problem does not have an optimal solution!");
+    }
+    // [END print_solution]
+
+    // [START advanced]
+    System.out.println("\nAdvanced usage:");
+    System.out.println("Problem solved in " + solver.getWallTime() + " seconds");
+    // [END advanced]
+  }
+
+  private CloneModelMb() {}
+}
+// [END program]