https://tomcat.apache.org/: Tomcat Core Logging Package 
public class org.apache.juli.JdkLoggerFormatter extends java.util.logging.Formatter
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: org.apache.juli.JdkLoggerFormatter
  super_class: java.util.logging.Formatter
{
  public static final int LOG_LEVEL_TRACE;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 400

  public static final int LOG_LEVEL_DEBUG;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 500

  public static final int LOG_LEVEL_INFO;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 800

  public static final int LOG_LEVEL_WARN;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 900

  public static final int LOG_LEVEL_ERROR;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 1000

  public static final int LOG_LEVEL_FATAL;
    descriptor: I
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: 1000

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.apache.juli.JdkLoggerFormatter this
         0: .line 40
            aload 0 /* this */
            invokespecial java.util.logging.Formatter.<init>:()V
            return
        end local 0 // org.apache.juli.JdkLoggerFormatter this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/apache/juli/JdkLoggerFormatter;

  public java.lang.String format(java.util.logging.LogRecord);
    descriptor: (Ljava/util/logging/LogRecord;)Ljava/lang/String;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=11, args_size=2
        start local 0 // org.apache.juli.JdkLoggerFormatter this
        start local 1 // java.util.logging.LogRecord record
         0: .line 52
            aload 1 /* record */
            invokevirtual java.util.logging.LogRecord.getThrown:()Ljava/lang/Throwable;
            astore 2 /* t */
        start local 2 // java.lang.Throwable t
         1: .line 53
            aload 1 /* record */
            invokevirtual java.util.logging.LogRecord.getLevel:()Ljava/util/logging/Level;
            invokevirtual java.util.logging.Level.intValue:()I
            istore 3 /* level */
        start local 3 // int level
         2: .line 54
            aload 1 /* record */
            invokevirtual java.util.logging.LogRecord.getLoggerName:()Ljava/lang/String;
            astore 4 /* name */
        start local 4 // java.lang.String name
         3: .line 55
            aload 1 /* record */
            invokevirtual java.util.logging.LogRecord.getMillis:()J
            lstore 5 /* time */
        start local 5 // long time
         4: .line 56
            aload 0 /* this */
            aload 1 /* record */
            invokevirtual org.apache.juli.JdkLoggerFormatter.formatMessage:(Ljava/util/logging/LogRecord;)Ljava/lang/String;
            astore 7 /* message */
        start local 7 // java.lang.String message
         5: .line 59
            aload 4 /* name */
            bipush 46
            invokevirtual java.lang.String.indexOf:(I)I
            iflt 7
         6: .line 60
            aload 4 /* name */
            aload 4 /* name */
            bipush 46
            invokevirtual java.lang.String.lastIndexOf:(I)I
            iconst_1
            iadd
            invokevirtual java.lang.String.substring:(I)Ljava/lang/String;
            astore 4 /* name */
         7: .line 63
      StackMap locals: org.apache.juli.JdkLoggerFormatter java.util.logging.LogRecord java.lang.Throwable int java.lang.String long java.lang.String
      StackMap stack:
            new java.lang.StringBuilder
            dup
            invokespecial java.lang.StringBuilder.<init>:()V
            astore 8 /* buf */
        start local 8 // java.lang.StringBuilder buf
         8: .line 65
            aload 8 /* buf */
            lload 5 /* time */
            invokevirtual java.lang.StringBuilder.append:(J)Ljava/lang/StringBuilder;
            pop
         9: .line 68
            iconst_0
            istore 9 /* i */
        start local 9 // int i
        10: goto 12
      StackMap locals: java.lang.StringBuilder int
      StackMap stack:
        11: aload 8 /* buf */
            ldc " "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            iinc 9 /* i */ 1
      StackMap locals:
      StackMap stack:
        12: iload 9 /* i */
            bipush 8
            aload 8 /* buf */
            invokevirtual java.lang.StringBuilder.length:()I
            isub
            if_icmplt 11
        end local 9 // int i
        13: .line 71
            iload 3 /* level */
            lookupswitch { // 5
                  400: 14
                  500: 15
                  800: 16
                  900: 17
                 1000: 18
              default: 19
          }
        14: .line 72
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc " T "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            goto 20
        15: .line 73
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc " D "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            goto 20
        16: .line 74
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc " I "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            goto 20
        17: .line 75
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc " W "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            goto 20
        18: .line 76
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc " E "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            goto 20
        19: .line 78
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            ldc "   "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        20: .line 83
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            aload 4 /* name */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        21: .line 84
            aload 8 /* buf */
            ldc " "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        22: .line 87
            iconst_0
            istore 9 /* i */
        start local 9 // int i
        23: goto 25
      StackMap locals: int
      StackMap stack:
        24: aload 8 /* buf */
            ldc " "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
            iinc 9 /* i */ 1
      StackMap locals:
      StackMap stack:
        25: iload 9 /* i */
            bipush 8
            aload 8 /* buf */
            invokevirtual java.lang.StringBuilder.length:()I
            isub
            if_icmplt 24
        end local 9 // int i
        26: .line 90
            aload 8 /* buf */
            aload 7 /* message */
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        27: .line 93
            aload 2 /* t */
            ifnull 34
        28: .line 94
            aload 8 /* buf */
            invokestatic java.lang.System.lineSeparator:()Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        29: .line 96
            new java.io.StringWriter
            dup
            sipush 1024
            invokespecial java.io.StringWriter.<init>:(I)V
            astore 9 /* sw */
        start local 9 // java.io.StringWriter sw
        30: .line 97
            new java.io.PrintWriter
            dup
            aload 9 /* sw */
            invokespecial java.io.PrintWriter.<init>:(Ljava/io/Writer;)V
            astore 10 /* pw */
        start local 10 // java.io.PrintWriter pw
        31: .line 98
            aload 2 /* t */
            aload 10 /* pw */
            invokevirtual java.lang.Throwable.printStackTrace:(Ljava/io/PrintWriter;)V
        32: .line 99
            aload 10 /* pw */
            invokevirtual java.io.PrintWriter.close:()V
        33: .line 100
            aload 8 /* buf */
            aload 9 /* sw */
            invokevirtual java.io.StringWriter.toString:()Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        end local 10 // java.io.PrintWriter pw
        end local 9 // java.io.StringWriter sw
        34: .line 103
      StackMap locals:
      StackMap stack:
            aload 8 /* buf */
            invokestatic java.lang.System.lineSeparator:()Ljava/lang/String;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            pop
        35: .line 105
            aload 8 /* buf */
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            areturn
        end local 8 // java.lang.StringBuilder buf
        end local 7 // java.lang.String message
        end local 5 // long time
        end local 4 // java.lang.String name
        end local 3 // int level
        end local 2 // java.lang.Throwable t
        end local 1 // java.util.logging.LogRecord record
        end local 0 // org.apache.juli.JdkLoggerFormatter this
      LocalVariableTable:
        Start  End  Slot     Name  Signature
            0   36     0     this  Lorg/apache/juli/JdkLoggerFormatter;
            0   36     1   record  Ljava/util/logging/LogRecord;
            1   36     2        t  Ljava/lang/Throwable;
            2   36     3    level  I
            3   36     4     name  Ljava/lang/String;
            4   36     5     time  J
            5   36     7  message  Ljava/lang/String;
            8   36     8      buf  Ljava/lang/StringBuilder;
           10   13     9        i  I
           23   26     9        i  I
           30   34     9       sw  Ljava/io/StringWriter;
           31   34    10       pw  Ljava/io/PrintWriter;
    MethodParameters:
        Name  Flags
      record  
}
SourceFile: "JdkLoggerFormatter.java"