Output functions and error handling

Most Java modeling objects have methods to query their attributes. For example, variable names and lower and upper bounds can be printed by using the getName, getLB, and getUB methods, respectively. This line prints the name of a variable and its bounds:

System.out.println(String.format("%s: [%s,%s]", frac[2].getName(), frac[2].getLB(),
      frac[2].getUB()));

The output is as follows:

 frac2: [0.0,0.3]

After the problem has been solved its solution value can be printed using frac[2].getSolution():

 frac2: 0.2

To create an object-oriented problem, an instance of the XpressProblem class is needed. Since an instance of XpressProblem wraps native resources, it is good practice to release these resources as soon as the object is no longer needed by using try-with-resources:

try (XpressProblem prob = new XpressProblem("Folio")) {
...
}

Problem attributes can be used to query the solution or solve statuses of the problem, by using getSolveStatus and getSolStatus , respectively.

System.out.println(String.format("Problem status:%n\tSolve status: %s%n\tSol status: %s",
                prob.attributes().getSolveStatus(), prob.attributes().getSolStatus()));

The method getSolStatus may be used to check the solution status. Only if the problem has been solved successfully Xpress will return or print out meaningful solution values.