java uses simple or primitive data types, such as int, char and Boolean etc. These data types are not part of the object hierarchy. They are passed by value to methods and cannot be directly passed by reference. However, at times there is a need to create an object representation of these simple data types. To address this need, Java provides classes that correspond to each of these simple types. These classes encapsulate, or wrap, the simple data type within a class. Thus, they are commonly referred to as wrapper classes.
Wrapper classes corresponding to respective simple data types are as given in table below.
Primitive Data Types
Wrapper class
byte
Byte
short
Short
int
Integer
long
Long
char
Character
float
Float
double
Double
boolean
Boolean
void
Void
eg
Say supposing there is a requirement to store only the
object in an array A.The Primitive types cannot be stored in
the same array as the array can accommodate only Objects
here is where Wrapper Class come into picture.ie, we create
wrapper for the primitive types.One such example is as below
Ex:int i;
Wrapper class for the primitive type(int) is created as below:
Integer i = new Integer();
without class non of the folder can run so the java program should start in class we can use the class without object in java
Class declaration
In C, no. In Java, yes.
The java interpreter or JVM (Java Virtual Machine) is not able to execute the java source code for a program. The java source code first needs to be compiled into bytecode that can be processed by JVM. Producing bytecode make the program platform independent as each platform has its own JVM. It is also possible to directly write bytecode, bypassing the need to compile, but that would be tedious job and also not good for security purpose as the compiler checks for various errors in a program.
The command to compile a Java program is "javac", followed by the class name (file name).
wrapper class is a predefined class .it is used for converting primitive data types into object type
without class non of the folder can run so the java program should start in class we can use the class without object in java
Nothing will happen. There is no restriction that every Java class must have a main method. The only program is that, this class cannot be executed as a standalone java program.
Class declaration
You can run a Java application from the command line using "java <name of the class>"
In C, no. In Java, yes.
Yes, executing a Java class will require memory just like any other program.
For run the program
The java interpreter or JVM (Java Virtual Machine) is not able to execute the java source code for a program. The java source code first needs to be compiled into bytecode that can be processed by JVM. Producing bytecode make the program platform independent as each platform has its own JVM. It is also possible to directly write bytecode, bypassing the need to compile, but that would be tedious job and also not good for security purpose as the compiler checks for various errors in a program.
The command to compile a Java program is "javac", followed by the class name (file name).
Because you are creating a class - a class in the sense of OOP.
The command is "java", followed by the class name. For example, if your compiled class is called myclass.class, you give the command: java myclass