https://openjdk.java.net/ 
public interface jdk.nashorn.internal.runtime.regexp.joni.Warnings
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: jdk.nashorn.internal.runtime.regexp.joni.Warnings
  super_class: java.lang.Object
{
  public static final java.lang.String INVALID_BACKREFERENCE;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "invalid back reference"

  public static final java.lang.String INVALID_SUBEXP_CALL;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "invalid subexp call"

  public static final java.lang.String INVALID_UNICODE_PROPERTY;
    descriptor: Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    ConstantValue: "invalid Unicode Property \\<%n>"
}
SourceFile: "Warnings.java"