Java version of the example

As is explained in Section Using the Optimizer with BCL Java, before accessing directly the problem held in Xpress Optimizer we need to initialize explicitly the Optimizer Java. The cut manager callback is implemented in Java by the class 'cutMgrListener'.

import java.io.*;
import com.dashoptimization.*;

public class xbcutex
{
 ...
 static XPRBvar[] start;
 static XPRB bcl;

 static class CutMgrCallback implements XPRScutMgrListener
 {
  public int XPRScutMgrEvent(XPRSprob oprob, Object data)
  {
   XPRBprob bprob;
   XPRBcut[] ca;
   int num,i;

   bprob = (XPRBprob)data;             /* Get the BCL problem */

   try
   {
    bprob.beginCB(oprob);              /* Coordinate BCL and Optimizer */
    num = oprob.getIntAttrib(XPRS.NODES);
    if(num == 2)                       /* Only generate cuts at node 2 */
    {
     ca = new XPRBcut[2];
     ca[0] = bprob.newCut(start[1].add(2) .lEql(start[0]), 2);
     ca[1] = bprob.newCut(start[2].mul(4) .add(start[3].mul(-5.3)) .lEql(-17), 2);
     System.out.println("Adding constraints:");
     for(i=0;i<2;i++) ca[i].print();
     bprob.addCuts(ca);
    }
    bprob.endCB();                     /* Reset BCL to main problem */
   }
   catch(XPRSprobException e)
   {
    System.out.println("Error  " + e.getCode() + ": " + e.getMessage());
   }
   return 0;                           /* Call this method once per node */
  }
 }

 public static void main(String[] args) throws XPRSexception
 {
  XPRBprob p;
  XPRSprob oprob;
  CutMgrCallback cb;

  bcl = new XPRB();                    /* Initialize BCL */
  p = bcl.newProb("Jobs");             /* Create a new problem */
  XPRS.init();                         /* Initialize Xpress Optimizer */

  start = new XPRBvar[4];              /* Create 'start' variables */
  for(j=0;j<4;j++) start[j] = p.newVar("start");
  ...                   /* Define constraints and an objective function */

  oprob = p.getXPRSprob();             /* Get Optimizer problem */
  p.setCutMode(1);                     /* Enable the cut mode */
  cb = new CutMgrCallback();
  oprob.addCutMgrListener(cb, p);      /* Def. the cut manager callback */
  p.mipOptimize();                     /* Solve the problem as MIP */
 ...                                   /* Solution output */
 }
}