Java Language
- Getting started with Java Language
- Top 10 Java Errors with Solutions
- Awesome Book
- Awesome Community
- Awesome Course
- Awesome Tutorial
- Awesome YouTube
- 2D Graphics in Java
- Alternative Collections
- Annotations
- Apache Commons Lang
- AppDynamics and TIBCO BusinessWorks Instrumentation for Easy Integration
- Applets
- Arrays
- Asserting
- Atomic Types
- Audio
- Autoboxing
- Basic Control Structures
- Benchmarks
- BigDecimal
- BigInteger
- Bit Manipulation
- BufferedWriter
- ByteBuffer
- Bytecode Modification
- C++ Comparison
- Calendar and its Subclasses
- Character encoding
- Choosing Collections
- Class - Java Reflection
- Classes and Objects
- Classloaders
- Collection Factory Methods
- Collections
- Command line Argument Processing
- Common Java Pitfalls
- Comparable and Comparator
- CompletableFuture
- Concurrent Collections
- Concurrent Programming (Threads)
- Console I/O
- Constructors
- Converting to and from Strings
- Creating Images Programmatically
- Currency and Money
- Date Class
- Dates and Time (java.time.*)
- Default Methods
- Dequeue Interface
- Disassembling and Decompiling
- Documenting Java Code
- Dynamic Method Dispatch
- Encapsulation
- Enum Map
- Enum starting with number
- Enums
- EnumSet class
- Exceptions and exception handling
- Executor, ExecutorService and Thread pools
- Expressions
- File I/O
- FileUpload to AWS
- Fluent Interface
- FTP (File Transfer Protocol)
- Functional Interfaces
- Generating Java Code
- Generics
- Getters and Setters
- Hashtable
- HttpURLConnection
- Immutable Class
- Immutable Objects
- Inheritance
- InputStreams and OutputStreams
- Installing Java (Standard Edition)
- Interfaces
- Iterator and Iterable
- Java Agents
- Java Compiler - 'javac'
- Java deployment
- Java Editions, Versions, Releases and Distributions
- Java Floating Point Operations
- Java Memory Management
- Java Memory Model
- Java Native Access
- Java Native Interface
- Java Performance Tuning
- Java Pitfalls - Exception usage
- Java Pitfalls - Language syntax
- Java Pitfalls - Nulls and NullPointerException
- Java Pitfalls - Performance Issues
- Java Pitfalls - Threads and Concurrency
- Java plugin system implementations
- Java Print Service
- Java SE 7 Features
- Java SE 8 Features
- Java Sockets
- Java Virtual Machine (JVM)
- JavaBean
- JAXB
- JAX-WS
- JMX
- JNDI
- JShell
- JSON in Java
- Just in Time (JIT) compiler
- JVM Flags
- JVM Tool Interface
- Lambda Expressions
- LinkedHashMap
- List vs SET
- Lists
- Literals
- Local Inner Class
- Localization and Internationalization
- LocalTime
- log4j / log4j2
- Logging (java.util.logging)
- Maps
- Modules
- Multi-Release JAR Files
- Nashorn JavaScript engine
- Nested and Inner Classes
- Networking
- New File I/O
- NIO - Networking
- Non-Access Modifiers
- NumberFormat
- Object Class Methods and Constructor
- Object Cloning
- Object References
- Operators
- Optional
- Oracle Official Code Standard
- Packages
- Parallel programming with Fork/Join framework
- Polymorphism
- Preferences
- Primitive Data Types
- Process
- Properties Class
- Queues and Deques
- Random Number Generation
- Readers and Writers
- Recursion
- Reference Data Types
- Reference Types
- Reflection API
- Regular Expressions
- Remote Method Invocation (RMI)
- Resources (on classpath)
- RSA Encryption
- Runtime Commands
- Scanner
- Carefully Closing a Scanner
- General Pattern that does most commonly asked about tasks
- Read an int from the command line
- Read the entire input as a String using Scanner
- Reading file input using Scanner
- Reading system input using Scanner
- Using custom delimiters
- Secure objects
- Security & Cryptography
- Security & Cryptography
- SecurityManager
- Serialization
- ServiceLoader
- Sets
- Singletons
- Sockets
- SortedMap
- Splitting a string into fixed length parts
- Stack-Walking API
- Streams
- String Tokenizer
- StringBuffer
- StringBuilder
- Strings
- sun.misc.Unsafe
- super keyword
- The Classpath
- The Java Command - 'java' and 'javaw'
- The java.util.Objects Class
- ThreadLocal
- TreeMap and TreeSet
- Type Conversion
- Unit Testing
- Using Other Scripting Languages in Java
- Using the static keyword
- Using ThreadPoolExecutor in MultiThreaded applications.
- Varargs (Variable Argument)
- Visibility (controlling access to members of a class)
- WeakHashMap
- XJC
- XML Parsing using the JAXP APIs
- XML XPath Evaluation
- XOM - XML Object Model
Java Language Scanner Carefully Closing a Scanner
Example
it can happen that you use a scanner with the System.in as parameter for the constructor, then you need to be aware that closing the scanner will close the InputStream too giving as next that every try to read the input on that (Or any other scanner object) will throw an java.util.NoSuchElementException or an java.lang.IllegalStateException
example:
Scanner sc1 = new Scanner(System.in);
Scanner sc2 = new Scanner(System.in);
int x1 = sc1.nextInt();
sc1.close();
// java.util.NoSuchElementException
int x2 = sc2.nextInt();
// java.lang.IllegalStateException
x2 = sc1.nextInt();
