What are wrapper classes?
As the name says, a wrapper class wraps (encloses) around a data type and gives it an object appearance. They are used to convert any primitive type into an object. The primitive data types are not objects; they do not belong to any class; they are defined in the language itself. Sometimes, it is required to convert data types into objects in Java language. For example, while storing in data structures which support only objects, it is required to convert the primitive type to object first, so we go for wrapper class. Example
int i = 500;
Integer iWrap = new Integer(i);
The int data type i is converted into an object, iWrap using Integer class. The iWrap object can be used in Java programming wherever i is required an object.
When you want to convert back (unwrap) to primitive type you can use intValue() of Integer class.
int j = iWrap.intValue();
System.out.println(j);
intValue() is a method of Integer class that returns an int data type.
Related Topics
- Java Interview Questions-Core Faq - 1
- Java Interview Questions-Core Faq - 2
- Java Interview Questions-Core Faq - 3
- Important features of Java
- Difference between Java and JavaScript?
- What is the difference between JDK and JRE?
- What gives Java its 'write once and run anywhere' nature?
- What is JVM and is it platform independent?
- What is Just-In-Time (JIT) compiler?
- What is the garbage collector in Java?
- What is NullPointerException in Java
- Difference between Stack and Heap memory in Java
- How to set the maximum memory usage for JVM?
- What is numeric promotion?
- Why do we need Generic Types in Java?
- What does it mean to be static in Java?
- What are final variables in Java?
- How Do Annotations Work in Java?
- How do I use the ternary operator in Java?
- What is instanceof keyword in Java?
- How ClassLoader Works in Java?
- What are fail-safe and fail-fast Iterators in Java
- What are method references?
- "Cannot Find Symbol" compile error
- Difference between system.gc() and runtime.gc()
- How to convert TimeStamp to Date in Java?
- Does garbage collection guarantee that a program will not run out of memory?
- How setting an Object to null help Garbage Collection?
- How do objects become eligible for garbage collection?
- How to calculate date difference in Java
- Difference between Path and Classpath
- Is Java "pass-by-reference" or "pass-by-value"?
- Difference between static and nonstatic methods java
- Why Java does not support pointers?
- What is package in Java?
- What is singleton class in Java?
- Difference between Java Local Variable, Instance Variable and a Class Variable?
- Can a top level class be private or protected in java
- Are Polymorphism , Overloading and Overriding similar concepts?
- How to Use Locks in Java
- Why Multiple Inheritance is Not Supported in Java
- Why Java is not a pure Object Oriented language?
- Why can't a Java class be declared as static?
- Difference between Abstract class and Interface in Java
- Why do I need to override the equals and hashCode methods in Java?
- Why does Java not support operator overloading?
- What’s meant by anonymous class in Java?
- Static Vs Dynamic class loading in Java
- Why am I getting a NoClassDefFoundError in Java?
- How to generate random integers within a specific range in Java
- What's the meaning of System.out.println in Java?
- What is the purpose of Runtime and System class?
- What is finally block in Java?
- What is difference between final, finally and finalize?
- What is try-with-resources in java?
- What is a stacktrace?
- What is the meaning of immutable in terms of String?
- What are different ways to create a string object in Java?
- Difference between String and StringBuffer/StringBuilder in Java
- What is the difference between creating String as new() and literal?
- How do I convert String to Date object in Java?
- How do I create a Java string from the contents of a file?
- What actually causes a StackOverflow error in Java?
- Why is char[] preferred over String for storage of password in Java
- What is I/O Filter and how do I use it in Java?
- Serialization and Deserialization in Java
- Understanding transient variables in Java
- What is Externalizable in Java?
- What is the purpose of serialization/deserialization in Java?
- What is the Difference between byte stream and Character streams
- How to append text to an existing file in Java
- Read/convert an InputStream to a String in Java
- What is the difference between Reader and InputStream in Java
- Introduction to Java threads
- What is synchronization Java?
- Static synchronization Vs non static synchronization in Java
- Java Thread Deadlock Tutorial
- What is Daemon thread in Java
- Difference between implements Runnable and extends Thread in Java
- What is the volatile keyword in Java
- What are the basic interfaces of Java Collections Framework
- What are the differences between ArrayList and Vector in Java
- What is the difference between ArrayList and LinkedList?
- What is the difference between List and Set in Java
- Difference between HashSet and HashMap in Java
- Difference between HashMap and Hashtable in Java?
- How does the hashCode() method of java works?
- Difference between capacity() and size() of Vector in Java
- What is a Java ClassNotFoundException?
- How to fix java.lang.UnsupportedClassVersionError