Java Language
- Getting started with Java Language
- Top 10 Java Errors with Solutions
- Awesome Book
- Awesome Community
- Awesome Course
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- 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
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- Bit Manipulation
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- C++ Comparison
- Calendar and its Subclasses
- Character encoding
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- Class - Java Reflection
- Classes and Objects
- Classloaders
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- Command line Argument Processing
- Common Java Pitfalls
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- Creating Images Programmatically
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- Date Class
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- Documenting Java Code
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- Expressions
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- Fluent Interface
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- Generating Java Code
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- Immutable Class
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- Inheritance
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- Interfaces
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- Java Agents
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- 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
- Pitfall - Calling 'new String(String)' is inefficient
- Pitfall - Calling System.gc() is inefficient
- Pitfall - Efficiency concerns with regular expressions
- Pitfall - Interning strings so that you can use == is a bad idea
- Pitfall - Iterating a Map's keys can be inefficient
- Pitfall - Over-use of primitive wrapper types is inefficient
- Pitfall - Small reads / writes on unbuffered streams are inefficient
- Pitfall - String concatenation in a loop does not scale
- Pitfall - The overheads of creating log messages
- Pitfall - Using 'new' to create primitive wrapper instances is inefficient
- Pitfall - Using size() to test if a collection is empty is inefficient.
- Java Pitfalls - Threads and Concurrency
- Java plugin system implementations
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- Maps
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- Oracle Official Code Standard
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- 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 Java Pitfalls - Performance Issues Pitfall - Using 'new' to create primitive wrapper instances is inefficient
Example
The Java language allows you to use new to create instances Integer, Boolean and so on, but it is generally a bad idea. It is better to either use autoboxing (Java 5 and later) or the valueOf method.
Integer i1 = new Integer(1); // BAD
Integer i2 = 2; // BEST (autoboxing)
Integer i3 = Integer.valueOf(3); // OK
The reason that using new Integer(int) explicitly is a bad idea is that it creates a new object (unless optimized out by JIT compiler). By contrast, when autoboxing or an explicit valueOf call are used, the Java runtime will try to reuse an Integer object from a cache of pre-existing objects. Each time the runtime has a cache "hit", it avoids creating an object. This also saves heap memory and reduces GC overheads caused by object churn.
Notes:
- In recent Java implementations, autoboxing is implemented by calling
valueOf, and there are caches forBoolean,Byte,Short,Integer,LongandCharacter. - The caching behavior for the integral types is mandated by the Java Language Specification.
