Program: 24588
Project: 24588
Buggy source:
public void doGraph(StaplerRequest req,StaplerResponse rsp) throws IOException {
  String category=req.getParameter("String_Node_Str");
  if (category == null) {
    throw new IOException("String_Node_Str");
  }
  if (ChartUtil.awtProblemCause != null) {
    rsp.sendRedirect2(req.getContextPath() + "String_Node_Str");
    return;
  }
  Calendar t=build.getTimestamp();
  if (req.checkIfModified(t,rsp)) {
    return;
  }
  DataSetBuilder<String,ChartUtil.NumberOnlyBuildLabel> dsb=new DataSetBuilder<String,ChartUtil.NumberOnlyBuildLabel>();
  int min=1000000, max=-110001100;
  String scale="String_Node_Str";
  for (MonKitBuildAction a=this; a != null; a=a.getPreviousResult()) {
    ChartUtil.NumberOnlyBuildLabel label=new ChartUtil.NumberOnlyBuildLabel(a.build);
    for (    MonKitCategory mkc : a.getMonKitCategories()) {
      if (mkc.getName().equalsIgnoreCase(category)) {
        for (        MonKitObservation mko : mkc) {
          Float f=new Float(mko.getValue());
          dsb.add(f,mko.getName(),label);
          System.out.println(mko.getName() + "String_Node_Str" + f.intValue());
          if (f.intValue() > max) {
            max=f.intValue() + 1;
          }
          if (f.intValue() < min) {
            min=f.intValue();
            if (min != 0) {
              min--;
            }
          }
          scale=mkc.getScale();
        }
      }
    }
  }
  ChartUtil.generateGraph(req,rsp,createChart(dsb.build(),category,scale,max,min),500,200);
}

Fixed version (ground truth):
public void doGraph(StaplerRequest req,StaplerResponse rsp) throws IOException {
  String category=req.getParameter("String_Node_Str");
  System.out.println("String_Node_Str" + category);
  if (category == null) {
    throw new IOException("String_Node_Str");
  }
  if (ChartUtil.awtProblemCause != null) {
    rsp.sendRedirect2(req.getContextPath() + "String_Node_Str");
    return;
  }
  Calendar t=build.getTimestamp();
  if (req.checkIfModified(t,rsp)) {
    return;
  }
  DataSetBuilder<String,ChartUtil.NumberOnlyBuildLabel> dsb=new DataSetBuilder<String,ChartUtil.NumberOnlyBuildLabel>();
  int min=1000000, max=-110001100;
  String scale="String_Node_Str";
  for (MonKitBuildAction a=this; a != null; a=a.getPreviousResult()) {
    ChartUtil.NumberOnlyBuildLabel label=new ChartUtil.NumberOnlyBuildLabel(a.build);
    for (    MonKitCategory mkc : a.getMonKitCategories()) {
      System.out.println("String_Node_Str" + mkc.getName());
      if (mkc.getName().equalsIgnoreCase(category)) {
        System.out.println("String_Node_Str");
        for (        MonKitObservation mko : mkc) {
          System.out.println("String_Node_Str" + mko.getName());
          Float f=new Float(mko.getValue());
          dsb.add(f,mko.getName(),label);
          System.out.println(mko.getName() + "String_Node_Str" + f.intValue());
          if (f.intValue() > max) {
            max=f.intValue() + 1;
          }
          if (f.intValue() < min) {
            min=f.intValue();
            if (min != 0) {
              min--;
            }
          }
          scale=mkc.getScale();
        }
      }
    }
  }
  System.out.println("String_Node_Str" + min + "String_Node_Str"+ max);
  ChartUtil.generateGraph(req,rsp,createChart(dsb.build(),category,scale,max,min),500,200);
}