http://xmlgraphics.apache.org/fop/: Apache FOP (Formatting Objects Processor) is the world's first print formatter driven by XSL formatting objects (XSL-FO) and the world's first output independent formatter. It is a Java application that reads a formatting object (FO) tree and renders the resulting pages to a specified output. Output formats currently supported include PDF, PCL, PS, AFP, TIFF, PNG, SVG, XML (area tree representation), Print, AWT and TXT. The primary output target is PDF. (Apache Software Foundation) 
class org.apache.fop.pdf.PDFLinearization$2 implements java.util.Comparator<org.apache.fop.pdf.PDFPage>
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.apache.fop.pdf.PDFLinearization$2
  super_class: java.lang.Object
{
  final org.apache.fop.pdf.PDFLinearization this$0;
    descriptor: Lorg/apache/fop/pdf/PDFLinearization;
    flags: (0x1010) ACC_FINAL, ACC_SYNTHETIC

  void <init>(org.apache.fop.pdf.PDFLinearization);
    descriptor: (Lorg/apache/fop/pdf/PDFLinearization;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.apache.fop.pdf.PDFLinearization$2 this
         0: .line 241
            aload 0 /* this */
            aload 1
            putfield org.apache.fop.pdf.PDFLinearization$2.this$0:Lorg/apache/fop/pdf/PDFLinearization;
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.apache.fop.pdf.PDFLinearization$2 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/apache/fop/pdf/PDFLinearization$2;
    MethodParameters:
        Name  Flags
      this$0  final

  public int compare(org.apache.fop.pdf.PDFPage, org.apache.fop.pdf.PDFPage);
    descriptor: (Lorg/apache/fop/pdf/PDFPage;Lorg/apache/fop/pdf/PDFPage;)I
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // org.apache.fop.pdf.PDFLinearization$2 this
        start local 1 // org.apache.fop.pdf.PDFPage o1
        start local 2 // org.apache.fop.pdf.PDFPage o2
         0: .line 243
            aload 1 /* o1 */
            getfield org.apache.fop.pdf.PDFPage.pageIndex:I
            invokestatic java.lang.Integer.valueOf:(I)Ljava/lang/Integer;
            aload 2 /* o2 */
            getfield org.apache.fop.pdf.PDFPage.pageIndex:I
            invokestatic java.lang.Integer.valueOf:(I)Ljava/lang/Integer;
            invokevirtual java.lang.Integer.compareTo:(Ljava/lang/Integer;)I
            ireturn
        end local 2 // org.apache.fop.pdf.PDFPage o2
        end local 1 // org.apache.fop.pdf.PDFPage o1
        end local 0 // org.apache.fop.pdf.PDFLinearization$2 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/apache/fop/pdf/PDFLinearization$2;
            0    1     1    o1  Lorg/apache/fop/pdf/PDFPage;
            0    1     2    o2  Lorg/apache/fop/pdf/PDFPage;
    MethodParameters:
      Name  Flags
      o1    
      o2    

  public int compare(java.lang.Object, java.lang.Object);
    descriptor: (Ljava/lang/Object;Ljava/lang/Object;)I
    flags: (0x1041) ACC_PUBLIC, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=3, locals=3, args_size=3
         0: .line 1
            aload 0
            aload 1
            checkcast org.apache.fop.pdf.PDFPage
            aload 2
            checkcast org.apache.fop.pdf.PDFPage
            invokevirtual org.apache.fop.pdf.PDFLinearization$2.compare:(Lorg/apache/fop/pdf/PDFPage;Lorg/apache/fop/pdf/PDFPage;)I
            ireturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
}
Signature: Ljava/lang/Object;Ljava/util/Comparator<Lorg/apache/fop/pdf/PDFPage;>;
SourceFile: "PDFLinearization.java"
EnclosingMethod: org.apache.fop.pdf.PDFLinearization.outputPages:(Ljava/io/OutputStream;)V
NestHost: org.apache.fop.pdf.PDFLinearization
InnerClasses:
  org.apache.fop.pdf.PDFLinearization$2