public class PageRankExample2 extends PageRanker {

  public PageRankExample2() {
    super( new String[] {"ID=1", "ID=2", "ID=3", "ID=4",
                         "ID=5", "ID=6", "ID=7"} );
    addLinks();
    setDampingFactor(1.0);
  }

  private void addLinks() {
    addLink("ID=1", "ID=2");
    addLink("ID=1", "ID=3");
    addLink("ID=1", "ID=5");
    addLink("ID=1", "ID=6");
    addLink("ID=2", "ID=1");
    addLink("ID=2", "ID=3");
    addLink("ID=2", "ID=4");
    addLink("ID=3", "ID=1");
    addLink("ID=3", "ID=4");
    addLink("ID=3", "ID=5");
    addLink("ID=4", "ID=1");
    addLink("ID=4", "ID=5");
    addLink("ID=5", "ID=1");
    addLink("ID=5", "ID=4");
    addLink("ID=5", "ID=6");
    addLink("ID=5", "ID=7");
    addLink("ID=6", "ID=5");
    addLink("ID=7", "ID=1");
  }

  public static void main(String[] args) throws Exception {
    PageRanker pr = new PageRankExample2();
    double[] ranks = pr.solve();
    print(pr.getPages(), ranks);
  }

  private static void print(String[] pages, double[] ranks) {
    int i = 0;
    for (String page : pages) {
      print(page, ranks[i++]);
    }
  }

  private static void print(String page, double rank) {
    System.out.printf("%s\t%.4f%n", page, rank);
  }
} 

$ java -classpath .:Jama-1.0.2.jar PageRankExample2

  1.000 -1.000 -0.500 -0.000 -0.250 -0.500 -0.000
 -0.200  1.000 -0.500 -0.333 -0.000 -0.000 -0.000
 -0.200 -0.000  1.000 -0.333 -0.250 -0.000 -0.000
 -0.200 -0.000 -0.000  1.000 -0.250 -0.000 -0.000
 -0.200 -0.000 -0.000 -0.333  1.000 -0.500 -1.000
 -0.000 -0.000 -0.000 -0.000 -0.250  1.000 -0.000
 -0.200 -0.000 -0.000 -0.000 -0.000 -0.000  1.000

Exception in thread "main" java.lang.RuntimeException: Matrix is singular.
        at Jama.LUDecomposition.solve(LUDecomposition.java:282)
        at Jama.Matrix.solve(Matrix.java:815)
        at PageRanker.solve(PageRanker.java:59)
        at PageRankExample2.main(PageRankExample2.java:33)
$ 

public class PageRanker {
  ...
  public double[] solve() {
    int len = pages.length;
    Matrix A = new Matrix(len,len);
    for (int j = 0; j < len; j++) {
      int n = 0;
      for (int i = 0; i < len; i++) {
        n += links[i][j];
      }
      double v = -1. * dampingFactor / (double)(n==0?(len-1):n);
      for (int i = 0; i < len; i++) {
        A.set(i, j, (i==j)?1.:((double)(n==0?1:links[i][j])*v));
      }
    }
    if (dampingFactor == 1.) {
      for (int j = 0; j < len; j++) {
        A.set(0, j, 1.);
      }
    }
    A.print(5,3);

    Matrix B = new Matrix(len,1);
    if (dampingFactor == 1.) {
      B.set(0, 0, 1.);
      for (int i = 1; i < len; i++) {
        B.set(i, 0, 0.);
      }
    }
    else {
      double v = (1. - dampingFactor) / (double)len;
      for (int i = 0; i < len; i++) {
        B.set(i, 0, v);
      }
    }   

    Matrix X = A.solve(B);

    double[] pageRanks = new double[len];
    for (int i = 0; i < len; i++) {
      pageRanks[i] = X.get(i, 0);
    }
    return pageRanks;
  }
}