https://github.com/google/guava/guava: Guava is a suite of core and expanded libraries that include utility classes, google's collections, io classes, and much much more. 
final class com.google.common.io.Files$FileByteSink extends com.google.common.io.ByteSink
  minor version: 0
  major version: 59
  flags: flags: (0x0030) ACC_FINAL, ACC_SUPER
  this_class: com.google.common.io.Files$FileByteSink
  super_class: com.google.common.io.ByteSink
{
  private final java.io.File file;
    descriptor: Ljava/io/File;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  private final com.google.common.collect.ImmutableSet<com.google.common.io.FileWriteMode> modes;
    descriptor: Lcom/google/common/collect/ImmutableSet;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL
    Signature: Lcom/google/common/collect/ImmutableSet<Lcom/google/common/io/FileWriteMode;>;

  private void <init>(java.io.File, com.google.common.io.FileWriteMode[]);
    descriptor: (Ljava/io/File;[Lcom/google/common/io/FileWriteMode;)V
    flags: (0x0082) ACC_PRIVATE, ACC_VARARGS
    Code:
      stack=2, locals=3, args_size=3
        start local 0 // com.google.common.io.Files$FileByteSink this
        start local 1 // java.io.File file
        start local 2 // com.google.common.io.FileWriteMode[] modes
         0: .line 185
            aload 0 /* this */
            invokespecial com.google.common.io.ByteSink.<init>:()V
         1: .line 186
            aload 0 /* this */
            aload 1 /* file */
            invokestatic com.google.common.base.Preconditions.checkNotNull:(Ljava/lang/Object;)Ljava/lang/Object;
            checkcast java.io.File
            putfield com.google.common.io.Files$FileByteSink.file:Ljava/io/File;
         2: .line 187
            aload 0 /* this */
            aload 2 /* modes */
            invokestatic com.google.common.collect.ImmutableSet.copyOf:([Ljava/lang/Object;)Lcom/google/common/collect/ImmutableSet;
            putfield com.google.common.io.Files$FileByteSink.modes:Lcom/google/common/collect/ImmutableSet;
         3: .line 188
            return
        end local 2 // com.google.common.io.FileWriteMode[] modes
        end local 1 // java.io.File file
        end local 0 // com.google.common.io.Files$FileByteSink this
      LocalVariableTable:
        Start  End  Slot   Name  Signature
            0    4     0   this  Lcom/google/common/io/Files$FileByteSink;
            0    4     1   file  Ljava/io/File;
            0    4     2  modes  [Lcom/google/common/io/FileWriteMode;
    MethodParameters:
       Name  Flags
      file   
      modes  

  public java.io.FileOutputStream openStream();
    descriptor: ()Ljava/io/FileOutputStream;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=5, locals=1, args_size=1
        start local 0 // com.google.common.io.Files$FileByteSink this
         0: .line 192
            new java.io.FileOutputStream
            dup
            aload 0 /* this */
            getfield com.google.common.io.Files$FileByteSink.file:Ljava/io/File;
            aload 0 /* this */
            getfield com.google.common.io.Files$FileByteSink.modes:Lcom/google/common/collect/ImmutableSet;
            getstatic com.google.common.io.FileWriteMode.APPEND:Lcom/google/common/io/FileWriteMode;
            invokevirtual com.google.common.collect.ImmutableSet.contains:(Ljava/lang/Object;)Z
            invokespecial java.io.FileOutputStream.<init>:(Ljava/io/File;Z)V
            areturn
        end local 0 // com.google.common.io.Files$FileByteSink this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/io/Files$FileByteSink;
    Exceptions:
      throws java.io.IOException

  public java.lang.String toString();
    descriptor: ()Ljava/lang/String;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=1, args_size=1
        start local 0 // com.google.common.io.Files$FileByteSink this
         0: .line 197
            new java.lang.StringBuilder
            dup
            ldc "Files.asByteSink("
            invokespecial java.lang.StringBuilder.<init>:(Ljava/lang/String;)V
            aload 0 /* this */
            getfield com.google.common.io.Files$FileByteSink.file:Ljava/io/File;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
            ldc ", "
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            aload 0 /* this */
            getfield com.google.common.io.Files$FileByteSink.modes:Lcom/google/common/collect/ImmutableSet;
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
            ldc ")"
            invokevirtual java.lang.StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
            invokevirtual java.lang.StringBuilder.toString:()Ljava/lang/String;
            areturn
        end local 0 // com.google.common.io.Files$FileByteSink this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/google/common/io/Files$FileByteSink;

  public java.io.OutputStream openStream();
    descriptor: ()Ljava/io/OutputStream;
    flags: (0x1041) ACC_PUBLIC, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=1, locals=1, args_size=1
         0: .line 1
            aload 0
            invokevirtual com.google.common.io.Files$FileByteSink.openStream:()Ljava/io/FileOutputStream;
            areturn
      LocalVariableTable:
        Start  End  Slot  Name  Signature
    Exceptions:
      throws java.io.IOException
}
SourceFile: "Files.java"
NestHost: com.google.common.io.Files
InnerClasses:
  private final FileByteSink = com.google.common.io.Files$FileByteSink of com.google.common.io.Files