A simple conclusion of some useful packages in java.

java.io

Classification by type of stream

Stream of characters

Reader

• BufferedReader
• InputStreamReader
  • FileReader
• StringReader
• PipedReader
• CharArrayReader
• FilterReader
  • PushbackReader

Writer

• BufferedWriter
• OutputStreamWriter
  • FileWriter
• PrinterWriter
• StringWriter
• PipedWriter
• CharArrayWriter
• FilterWriter

Stream of bytes

InputStream

• FileInputStream
• FilterInputStream
  • BufferedInputStream
  • DataInputStream
  • PushbackInputStream
• ObjectInputStream
• PipedInputStream
• SequenceInputStream
• StringBufferInputStream
• ByteArrayInputStream

OutputStream

• FileOutputStream
• FilterOutputStream
  • BufferedOutputStream
  • DataOutputStream
  • PrintStream
• ObjectOutputStream
• PipedOutputStream
• ByteArrayOutputStream

Classification by operation object

File

• FileReader
• FileWriter
• FileInputStream
• FileOutputStream

Array

ByteArray

• ByteArrayInputStream
• ByteArrayOutputStream

CharArray

• CharArrayReader
• CharArrayWriter

Pipe

• PipedReader
• PipedWriter
• PipedInputStream
• PipedOutputStream

Data (basic data types)

• DataInputStream
• DataOutputStream

Buffer

• BufferedReader
• BufferedWriter
• BufferedInputStream
• BufferedOutputStream

Print

• PrinterWriter
• PrintStream

Object serialization

• ObjectInputStream
• ObjectOutputStream

Stream transformation

• InputStreamReader
• OutputStreamWriter

java.lang

System

Process

• Process
• ProcessBuilder

Thread

• Thread
• ThreadGroup
• ThreadDeath
• ThreadLocal

Run

• Runnable
• Runtime
• RuntimePermission
• System

Stack

• StackTraceElement

Exception - Throwable

Error

• NoClassDefFoundError
• NoSuchFieldError
• OutOfMemoryError
• NoSuchMethodError

Exception

• ArrayIndexOutOfBoundsException
• ClassCastException
• ClassNotFoundException
• IllegalArgumentException
• IndexOutOfBoundsException
• NoSuchFieldException
• NoSuchMethodException
• NullPointerException
• NumberFormatException
• RuntimeException
• InterruptedException

Annotation

java.lang

• Deprecated
• FunctionalInterface
• Override
• SafeVarargs
• SuppressWarnings

java.lang.annotation

• Documented
• Inherited
• Native
• Repeatable
• Retention
• Target

Interface

java.lang

• AutoCloseable
• Annotation
• CharSequence
• Cloneable
• Comparable
• Iterable
• Readable
• Runnable

java.lang.reflect

• InvocationHandler
• GenericDeclaration
• AnnotatedElement
• Member

Type

Basic type

• Boolean
• Character
• String
• Number
  • Byte
  • Short
  • Integer
  • Long
  • Float
  • Double

Class

• Class

Package

• Package

Other

• Object
• Enum
• Void

Tool class

Character serial

• StringBuffer
• StringBuilder

Math

• java.lang.Math

NOTICE: not java.math

Reflection

java.lang.reflect

• Array
• Constructor
• Field
• Method
• Proxy
• Executable
• AccessibleObject

java.math

NOTICE: not java.lang.Math

• BigDecimal
• BigInteger
• MathContext
• RoundingMode

To be continued

java.net