https://xerces.apache.org/xerces2-j/: Xerces2 is the next generation of high performance, fully compliant XML parsers in the Apache Xerces family. This new version of Xerces introduces the Xerces Native Interface (XNI), a complete framework for building parser components and configurations that is extremely modular and easy to program. The Apache Xerces2 parser is the reference implementation of XNI but other parser components, configurations, and parsers can be written using the Xerces Native Interface. For complete design and implementation documents, refer to the XNI Manual. Xerces2 is a fully conforming XML Schema 1.0 processor. A partial experimental implementation of the XML Schema 1.1 Structures and Datatypes Working Drafts (December 2009) and an experimental implementation of the XML Schema Definition Language (XSD): Component Designators (SCD) Candidate Recommendation (January 2010) are provided for evaluation. For more information, refer to the XML Schema page. Xerces2 also provides a complete implementation of the Document Object Model Level 3 Core and Load/Save W3C Recommendations and provides a complete implementation of the XML Inclusions (XInclude) W3C Recommendation. It also provides support for OASIS XML Catalogs v1.1. Xerces2 is able to parse documents written according to the XML 1.1 Recommendation, except that it does not yet provide an option to enable normalization checking as described in section 2.13 of this specification. It also handles namespaces according to the XML Namespaces 1.1 Recommendation, and will correctly serialize XML 1.1 documents if the DOM level 3 load/save APIs are in use. 
public class org.apache.xerces.impl.msg.XMLMessageFormatter implements org.apache.xerces.util.MessageFormatter
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.apache.xerces.impl.msg.XMLMessageFormatter
  super_class: java.lang.Object
{
  public static final java.lang.String XML_DOMAIN;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/TR/1998/REC-xml-19980210"

  public static final java.lang.String XMLNS_DOMAIN;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "http://www.w3.org/TR/1999/REC-xml-names-19990114"

  private java.util.Locale fLocale;
    descriptor: Ljava/util/Locale;
    flags: (0x0002) ACC_PRIVATE

  private java.util.ResourceBundle fResourceBundle;
    descriptor: Ljava/util/ResourceBundle;
    flags: (0x0002) ACC_PRIVATE

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // org.apache.xerces.impl.msg.XMLMessageFormatter this
         0: .line 36
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
         1: .line 44
            aload 0 /* this */
            aconst_null
            putfield org.apache.xerces.impl.msg.XMLMessageFormatter.fLocale:Ljava/util/Locale;
         2: .line 45
            aload 0 /* this */
            aconst_null
            putfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
         3: .line 36
            return
        end local 0 // org.apache.xerces.impl.msg.XMLMessageFormatter this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    4     0  this  Lorg/apache/xerces/impl/msg/XMLMessageFormatter;

  public java.lang.String formatMessage(java.util.Locale, java.lang.String, java.lang.Object[]);
    descriptor: (Ljava/util/Locale;Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/String;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=5, locals=7, args_size=4
        start local 0 // org.apache.xerces.impl.msg.XMLMessageFormatter this
        start local 1 // java.util.Locale locale
        start local 2 // java.lang.String key
        start local 3 // java.lang.Object[] arguments
         0: .line 69
            aload 1 /* locale */
            ifnonnull 2
         1: .line 70
            invokestatic java.util.Locale.getDefault:()Ljava/util/Locale;
            astore 1 /* locale */
         2: .line 72
      StackMap locals:
      StackMap stack:
            aload 1 /* locale */
            aload 0 /* this */
            getfield org.apache.xerces.impl.msg.XMLMessageFormatter.fLocale:Ljava/util/Locale;
            if_acmpeq 5
         3: .line 73
            aload 0 /* this */
            ldc "org.apache.xerces.impl.msg.XMLMessages"
            aload 1 /* locale */
            invokestatic java.util.ResourceBundle.getBundle:(Ljava/lang/String;Ljava/util/Locale;)Ljava/util/ResourceBundle;
            putfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
         4: .line 75
            aload 0 /* this */
            aload 1 /* locale */
            putfield org.apache.xerces.impl.msg.XMLMessageFormatter.fLocale:Ljava/util/Locale;
         5: .line 81
      StackMap locals:
      StackMap stack:
            aload 0 /* this */
            getfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
            aload 2 /* key */
            invokevirtual java.util.ResourceBundle.getString:(Ljava/lang/String;)Ljava/lang/String;
            astore 4 /* msg */
        start local 4 // java.lang.String msg
         6: .line 82
            aload 3 /* arguments */
            ifnull 16
         7: .line 84
            aload 4 /* msg */
            aload 3 /* arguments */
            invokestatic java.text.MessageFormat.format:(Ljava/lang/String;[Ljava/lang/Object;)Ljava/lang/String;
            astore 4 /* msg */
         8: .line 85
            goto 16
         9: .line 86
      StackMap locals: org.apache.xerces.impl.msg.XMLMessageFormatter java.util.Locale java.lang.String java.lang.Object[] java.lang.String
      StackMap stack: java.lang.Exception
            pop
        10: .line 87
            aload 0 /* this */
            getfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
            ldc "FormatFailed"
            invokevirtual java.util.ResourceBundle.getString:(Ljava/lang/String;)Ljava/lang/String;
            astore 4 /* msg */
        11: .line 88
            new java.lang.StringBuilder
            dup
            aload 4 /* msg */
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            ldc " "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            aload 0 /* this */
            getfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
            aload 2 /* key */
            invokevirtual java.util.ResourceBundle.getString:(Ljava/lang/String;)Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            astore 4 /* msg */
        12: .line 91
            goto 16
        end local 4 // java.lang.String msg
        13: .line 94
      StackMap locals: org.apache.xerces.impl.msg.XMLMessageFormatter java.util.Locale java.lang.String java.lang.Object[]
      StackMap stack: java.util.MissingResourceException
            pop
        14: .line 95
            aload 0 /* this */
            getfield org.apache.xerces.impl.msg.XMLMessageFormatter.fResourceBundle:Ljava/util/ResourceBundle;
            ldc "BadMessageKey"
            invokevirtual java.util.ResourceBundle.getString:(Ljava/lang/String;)Ljava/lang/String;
            astore 4 /* msg */
        start local 4 // java.lang.String msg
        15: .line 96
            new java.util.MissingResourceException
            dup
            aload 2 /* key */
            aload 4 /* msg */
            aload 2 /* key */
            invokespecial java.util.MissingResourceException.<init>:(Ljava/lang/String;Ljava/lang/String;Ljava/lang/String;)V
            athrow
        16: .line 100
      StackMap locals: java.lang.String
      StackMap stack:
            aload 4 /* msg */
            ifnonnull 28
        17: .line 101
            aload 2 /* key */
            astore 4 /* msg */
        18: .line 102
            aload 3 /* arguments */
            arraylength
            ifle 28
        19: .line 103
            new java.lang.StringBuffer
            dup
            aload 4 /* msg */
            invokespecial java.lang.StringBuffer.<init>:(Ljava/lang/String;)V
            astore 5 /* str */
        start local 5 // java.lang.StringBuffer str
        20: .line 104
            aload 5 /* str */
            bipush 63
            invokevirtual java.lang.StringBuffer.append:(C)Ljava/lang/StringBuffer;
            pop
        21: .line 105
            iconst_0
            istore 6 /* i */
        start local 6 // int i
        22: goto 27
        23: .line 106
      StackMap locals: java.lang.StringBuffer int
      StackMap stack:
            iload 6 /* i */
            ifle 25
        24: .line 107
            aload 5 /* str */
            bipush 38
            invokevirtual java.lang.StringBuffer.append:(C)Ljava/lang/StringBuffer;
            pop
        25: .line 109
      StackMap locals:
      StackMap stack:
            aload 5 /* str */
            aload 3 /* arguments */
            iload 6 /* i */
            aaload
            invokestatic java.lang.String.valueOf:(Ljava/lang/Object;)Ljava/lang/String;
            invokevirtual java.lang.StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
            pop
        26: .line 105
            iinc 6 /* i */ 1
      StackMap locals:
      StackMap stack:
        27: iload 6 /* i */
            aload 3 /* arguments */
            arraylength
            if_icmplt 23
        end local 6 // int i
        end local 5 // java.lang.StringBuffer str
        28: .line 114
      StackMap locals:
      StackMap stack:
            aload 4 /* msg */
            areturn
        end local 4 // java.lang.String msg
        end local 3 // java.lang.Object[] arguments
        end local 2 // java.lang.String key
        end local 1 // java.util.Locale locale
        end local 0 // org.apache.xerces.impl.msg.XMLMessageFormatter this
      LocalVariableTable:
        Start  End  Slot       Name  Signature
            0   29     0       this  Lorg/apache/xerces/impl/msg/XMLMessageFormatter;
            0   29     1     locale  Ljava/util/Locale;
            0   29     2        key  Ljava/lang/String;
            0   29     3  arguments  [Ljava/lang/Object;
            6   13     4        msg  Ljava/lang/String;
           15   29     4        msg  Ljava/lang/String;
           20   28     5        str  Ljava/lang/StringBuffer;
           22   28     6          i  I
      Exception table:
        from    to  target  type
           7     8       9  Class java.lang.Exception
           5    12      13  Class java.util.MissingResourceException
    Exceptions:
      throws java.util.MissingResourceException
    MethodParameters:
           Name  Flags
      locale     
      key        
      arguments  
}
SourceFile: "XMLMessageFormatter.java"