Program: 40138
Project: 40138
Buggy source:
public void substitute(Position range,String newText){
  int startLine=range.getFirstLine() - p.getFirstLine();
  int endLine=range.getLastLine() - p.getFirstLine();
  if (startLine != endLine) {
    String newLines[]=new String[lines.length - (endLine - startLine)];
    int i=0;
    while (i < startLine) {
      newLines[i]=lines[i];
      i++;
    }
    newLines[i++]=lines[startLine].substring(0,range.getFirstCol()) + lines[endLine].substring(range.getLastCol());
    while (i < newLines.length) {
      newLines[i]=lines[i + (endLine - startLine)];
      i++;
    }
    lines=newLines;
    endLine=startLine;
    final Position hack=range;
    range=new AbstractSourcePosition(){
      @Override public int getFirstLine(){
        return hack.getFirstLine();
      }
      @Override public int getLastLine(){
        return hack.getFirstLine();
      }
      @Override public int getFirstCol(){
        return hack.getFirstCol();
      }
      @Override public int getLastCol(){
        return hack.getFirstCol();
      }
      @Override public int getFirstOffset(){
        return hack.getFirstOffset();
      }
      @Override public int getLastOffset(){
        return hack.getFirstOffset();
      }
      @Override public URL getURL(){
        return hack.getURL();
      }
      @Override public InputStream getInputStream() throws IOException {
        return hack.getInputStream();
      }
    }
;
  }
  String[] newTextLines=newText.split("String_Node_Str");
  if (newTextLines.length == 1) {
    lines[startLine]=lines[startLine].substring(0,range.getFirstCol()) + newTextLines[0] + lines[startLine].substring(range.getLastCol() + 1);
  }
 else {
    String[] newLines=new String[lines.length + newTextLines.length - 1];
    int i=0;
    while (i < startLine) {
      newLines[i]=lines[i];
      i++;
    }
    newLines[i++]=lines[startLine].substring(0,range.getFirstCol()) + newTextLines[0];
    for (int j=1; j < newTextLines.length - 1; j++) {
      lines[i++]=newTextLines[j];
    }
    newLines[i++]=newTextLines[newTextLines.length - 1] + lines[endLine].substring(range.getLastCol() + 1);
    while (i < newLines.length) {
      newLines[i]=lines[i - newTextLines.length + 1];
      i++;
    }
    lines=newLines;
  }
}

Fixed version (ground truth):
public void substitute(Position range,String newText){
  int startLine=range.getFirstLine() - p.getFirstLine();
  int endLine=range.getLastLine() - p.getFirstLine();
  if (startLine != endLine) {
    String newLines[]=new String[lines.length - (endLine - startLine)];
    int i=0;
    while (i < startLine) {
      newLines[i]=lines[i];
      i++;
    }
    newLines[i++]=lines[startLine].substring(0,range.getFirstCol()) + lines[endLine].substring(range.getLastCol());
    while (i < newLines.length) {
      newLines[i]=lines[i + (endLine - startLine)];
      i++;
    }
    lines=newLines;
    endLine=startLine;
    final Position hack=range;
    range=new AbstractSourcePosition(){
      @Override public int getFirstLine(){
        return hack.getFirstLine();
      }
      @Override public int getLastLine(){
        return hack.getFirstLine();
      }
      @Override public int getFirstCol(){
        return hack.getFirstCol();
      }
      @Override public int getLastCol(){
        return hack.getFirstCol();
      }
      @Override public int getFirstOffset(){
        return hack.getFirstOffset();
      }
      @Override public int getLastOffset(){
        return hack.getFirstOffset();
      }
      @Override public URL getURL(){
        return hack.getURL();
      }
      @Override public Reader getReader() throws IOException {
        return hack.getReader();
      }
    }
;
  }
  String[] newTextLines=newText.split("String_Node_Str");
  if (newTextLines.length == 1) {
    lines[startLine]=lines[startLine].substring(0,range.getFirstCol()) + newTextLines[0] + lines[startLine].substring(range.getLastCol() + 1);
  }
 else {
    String[] newLines=new String[lines.length + newTextLines.length - 1];
    int i=0;
    while (i < startLine) {
      newLines[i]=lines[i];
      i++;
    }
    newLines[i++]=lines[startLine].substring(0,range.getFirstCol()) + newTextLines[0];
    for (int j=1; j < newTextLines.length - 1; j++) {
      lines[i++]=newTextLines[j];
    }
    newLines[i++]=newTextLines[newTextLines.length - 1] + lines[endLine].substring(range.getLastCol() + 1);
    while (i < newLines.length) {
      newLines[i]=lines[i - newTextLines.length + 1];
      i++;
    }
    lines=newLines;
  }
}