System is class of Lang Package.
System class is final .you can not able to extends to this Class .
The Constructor of system class is private .So you can not initialize this class .
PrintSteam is class in io package for responsible for give out and take input to console .
println() method is define in PrintSteam Class not System class .
and one of the limitation for PrintStream class is that you can not direct used PrintStream method with out help of System class .
We call all PrintStream method using System class .
out is reference variable of Print stream class and out is belonging to class not object .it means out is static .out is static,final reference variable of printstream .
Declaration of out In system is following
public final static PrintStream out;
Demonstration Of System.out.println()
1-We need a class which Proto type same as System class .
Class Name is WorkAsSystem ;
and constructor is private WorkAsSystem() ;
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package lang.example;//package like java.lang
public final class WorkAsSystem {//Similar To System Class
public static final WorkAsPrintStreamoutexample=forCreateNewWorkAsPRintStreamObject();//similar to out variable
private WorkAsSystem() { }
private static WorkAsPrintStream forCreateNewWorkAPRintStreamObject()
{
return new WorkAsPrintStream();
}
}
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2-We need as class which Proto type is PrintStream class
Class name is :WorkAsPrintStream
3-We also define a method same as println() in this class
method name is printlnexample();
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package io.example;//package like java.io ;
public class WorkAsPrintStream {//similar to PrintStream
public WorkAsPrintStream() {
}
public void printlnexample()
{
System.out.println("This is example of System.out.println();");
}
}
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4-Create a class which used this method as System.out.println();
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package example.example;
import lang.example;
public class Example
{
public Example()
{}
public static void main(String[] args)
{
WorkAsSystem.outexample.printlnexample();
}
}
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5-out is
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This is example of System.out.println();
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* if you can define a variable as a final then you need to initialization as define time . so out is final then we need to initialization by a private static method which is just create a new Object for PrintStream Class . to help to call method of printstream class .
