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Requiring multiple upper bounds extends A B

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You can require a generic type to extend multiple upper bounds.

Example: we want to sort a list of numbers but Number doesn’t implement Comparable. 

public <T extends Number & Comparable<T>> void sortNumbers( List<T> n ) {
  Collections.sort( n );
}

In this example T must extend Number and implement Comparable<T> which should fit all “normal” built-in number implementations like Integer or BigDecimal but doesn’t fit the more exotic ones like Striped64.

Since multiple inheritance is not allowed, you can use at most one class as a bound and it must be the first listed. For example, <T extends Comparable<T> & Number> is not allowed because Comparable is an interface, and not a class.

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Generics:
* Generics
* Creating a Generic Class
* Deciding between T super T and extends T
* The Diamond
* Declaring a Generic Method
* Requiring multiple upper bounds extends A B
* Instantiating a generic type
* Benefits of Generic class and interface
* Obtain class that satisfies generic parameter at runtime
* Creating a Bounded Generic Class
* Referring to the declared generic type within its own declaration
* Using Generics to auto-cast
* Binding generic parameter to more than 1 type
* Use of instanceof with Generics
* Different ways for implementing a Generic Interface or extending a Generic Class
Table Of Contents
0 Inheritance
1 Getting started with Java
2 Streams
3 Exceptions
4 Collections
5 Lambda Expressions
6 Generics
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25 JAXB
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34 Calendar and its Subclasses
35 Nashorn JavaScript engine
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38 Iterator and Iterable
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62 ThreadLocal
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66 Resources on classpath
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69 Oracle Official Code Standard
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80 JVM Tool Interface
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82 Apache Commons Lang
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84 The Classpath
85 Bytecode Modification
86 XML Parsing using JAXP
87 Reference Types
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90 XML XPath Evaluation
91 Performance Tuning
92 Parallel programming with ForkJoin framework
93 Common Pitfalls
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95 Java Compiler
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97 Installing Java Standard Edition
98 Process
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100 Dates and Time using java.time
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103 Just in Time JIT compiler
104 FTP File Transfer Protocol
105 Java Native Access JNI
106 Modules
107 Pitfalls - exceptions
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109 ServiceLoader
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111 Object References
112 Pitfalss - performance
113 Creating Images Programmatically
114 Applets
115 NIO Networking
116 New File I/O
117 Secure objects
118 Pitfalls - threads and concurrency
119 Splitting a string into fixed length parts
120 Pitfalls - nulls and NullPointerException
121 SecurityManager
122 JNDI
123 super keyword
124 java.util.Objects class
125 Java command: java and javaw
126 Atomic types
127 Floating Point Operations
128 Converting to and from strings
129 sun.misc.Unsafe
130 Java Memory Model
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133 Queues and deques
134 Runtime commands
135 NumberFormat
136 Security and Cryptograhy
137 Java Virtual Machine JVM
138 Unit Testing
139 JavaBean
140 Expressions
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142 Java SE 8 Features
143 Java SE 7 Features
144 Packages
145 Concurrency and Money
146 Concurrent Collections
147 Using ThreadPoolExecutor in multi-threaded applications
148 Java Editions, versions, releases and distributions
149 Dynamic method dispatch
150 JMX
151 Security and cryptography
152 Generating Java Code
153 JShell
154 Benchmarks
155 Collection Factory Methods
156 Multi-release JAR files
157 Stack-Walking API
158 TreeMap and TreeSet
159 Sockets
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161 Using other scripting languages in Java
162 Functional interfaces
163 List vs. set
164 2D graphics
165 Reflection
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169 Local Inner class
170 Java Print Service
171 Immutable class
172 String Tokenizer
173 File upload to S3 / AWS
174 Readers and writers
175 Hashtable
176 Enum starting with a number
177 SortedMap
178 WeakHashMap
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180 StringBuffer
181 Choosing Collections
182 C++ Comparison
183 CompletableFuture
184 Contributors