wrapper classes in java
Wrapper classes: classes that are dedicated to primitives
Byte, Short, Integer, Long, Float, Double, Character, Boolean
presented in "java.lang" package
AutoBoxing: converting primitive values to wrapper class
int a = 100;
Integer b = a // auto boxing
Unboxing: converting wrapper class value to primitives
Integer a = 100;
int b = a; // unboxing
int a = 100;
double b = a; // nonewrapper classes in java ebhor.com
public class CommandLineArguments {
public static void main(String[] args) {
int a = Integer.parseInt(args[0]);
int b = Integer.parseInt(args[1]);
int sum = a + b;
System.out.println("Sum is " + sum);
}
}What are the primitives and wrapper classes in java?
In Java, for each Primitive type, there is a matching class type.
We call them Wrapper classes:
Primitive types are the most basic data types
available within the Java language.
There are 8: boolean , byte , char , short ,
int , long , float and double .
These types serve as the building blocks of
data manipulation in Java.
Wrapper classes: Byte, Short, Integer, Long,
Float, Double, Boolean, Character
All the wrapper classes are subclasses
of the abstract class Number.
The object of the wrapper class contains or
wraps its respective primitive data type.
Converting primitive data types into object
is called boxing, and this is taken care by the compiler.
Differences:
1. Wrappers classes are object
2. null can only be assigned to classes
3. Wrapper class does have methods
4. Primitives does have default values
default value of primitives:
byte, short, int, long ==> 0
float, double ==> 0.0;
boolean ==> false;
char ==> space
5. Default values of wrapper class: nullJava wrapper classes
ArrayList<int> myNumbers = new ArrayList<int>(); // InvalidJava wrapper classes
ArrayList<Integer> myNumbers = new ArrayList<Integer>(); // ValidWrapper classes in java
public class WrapperClassExample
{
public static void main(String[] args)
{
// before java 5 version
int num = 70;
// we were converting explicitly like this
Integer i = Integer.valueOf(num);
// printing Integer object value explicitly
System.out.println(i);
// in java 5 version
// Autoboxing and unboxing feature was introduced
// now there is no need of explicit conversion
Integer i1 = num;
System.out.println(i1);
}
}Copyright © 2021 Codeinu
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