Run code only if there is a value present

suggest change

Optional<String> optionalWithValue = Optional.of("foo");
optionalWithValue.ifPresent(System.out::println);//Prints "foo".

Optional<String> emptyOptional = Optional.empty();
emptyOptional.ifPresent(System.out::println);//Does nothing.

Found a mistake? Have a question or improvement idea? Let me know.

Optional:

*Optional

*Map

*Return default value if Optional is empty

*Throw an exception if there is no value

*Lazily provide a default value using a Supplier

*Filter

*Using Optional containers for primitive number types

*Run code only if there is a value present

*FlatMap

Table Of Contents

0Inheritance

1Getting started with Java

10Maps

11Strings

12InputStreams and OutputStreams

13Default Methods

14Classes and Objects

15Basic Control structures

16Concurrent Programming Threads

17Console I/O

18Singletons

19Visibility controlling access to members of a class

20Regular Expressions

21Autoboxing

22Documenting Java Code

23Executor, ExecutorService and Thread pools

24Object Class Methods and Constructor

25JAXB

26Primitive Data Types

27Networking

28Optional

29Enums

30HttpURLConnection

31Annotations

32Audio

33Data Class

34Calendar and its Subclasses

35Nashorn JavaScript engine

36Java Native Interface (JNI)

37Remote Method Invocation (RMI)

38Iterator and Iterable

41Scanner

49Random Number Generation

50Recursion

51Polymorphism

52StringBuilder

53Refernce Data Types

61Varargs Variable Arguments

62ThreadLocal

63Logging

64static keyword

65Disassembling and Decompling

66Resources on classpath

67log4j, log4j2

68JVM Flags

69Oracle Official Code Standard

70Character encoding

71Java Memory Management

72Immutable Objects

73Object Cloning

74Alternative Collections

75Lists

76BufferedWriter

77LocalTime

78Sets

79Comparable and Comparator

80JVM Tool Interface

81Nested and Inner Classes

82Apache Commons Lang

83Getters and Setter

84The Classpath

85Bytecode Modification

86XML Parsing using JAXP

87Reference Types

88Localization and Internationalization

89JAX-WS

90XML XPath Evaluation

91Performance Tuning

92Parallel programming with ForkJoin framework

93Common Pitfalls

94Non-Access Modifiers

95Java Compiler

96XJC

97Installing Java Standard Edition

98Process

99Command line argument processing

100Dates and Time using java.time

101Fluent Interface

102XOM - XML Object Model

103Just in Time JIT compiler

104FTP File Transfer Protocol

105Java Native Access JNI

106Modules

107Pitfalls - exceptions

108Pitfalls - language syntax

109ServiceLoader

110ClasssLoader

111Object References

112Pitfalss - performance

113Creating Images Programmatically

114Applets

115NIO Networking

116New File I/O

117Secure objects

118Pitfalls - threads and concurrency

119Splitting a string into fixed length parts

120Pitfalls - nulls and NullPointerException

121SecurityManager

122JNDI

123super keyword

124java.util.Objects class

125Java command: java and javaw

126Atomic types

127Floating Point Operations

128Converting to and from strings

129sun.misc.Unsafe

130Java Memory Model

131Java deployment

132Java plugin system implementations

133Queues and deques

134Runtime commands

135NumberFormat

136Security and Cryptograhy

137Java Virtual Machine JVM

138Unit Testing

139JavaBean

140Expressions

141Literals

142Java SE 8 Features

143Java SE 7 Features

144Packages

145Concurrency and Money

146Concurrent Collections

147Using ThreadPoolExecutor in multi-threaded applications

148Java Editions, versions, releases and distributions

149Dynamic method dispatch

150JMX

151Security and cryptography

152Generating Java Code

153JShell

154Benchmarks

155Collection Factory Methods

156Multi-release JAR files

157Stack-Walking API

158TreeMap and TreeSet

159Sockets

160Java Sockets

161Using other scripting languages in Java

162Functional interfaces

163List vs. set

1642D graphics

165Reflection

166Deque interface

167Enum Map

168EnumSet class

169Local Inner class

170Java Print Service

171Immutable class

172String Tokenizer

173File upload to S3 / AWS

174Readers and writers

175Hashtable

176Enum starting with a number

177SortedMap

178WeakHashMap

179LinkedHashMap

180StringBuffer

181Choosing Collections

182C++ Comparison

183CompletableFuture

184Contributors