Question

I will have to be using JavaCompilers in the near future so I am trying to learn about the basics now and choose the best one to learn and I have come across a question that i could not really fine an answer to online

At the moment im looking at the JavaCompiler. If i have a program X being evaluated and it takes input from System.in and prints output to System.out,
can I compile and run it while feeding it some specific input and capturing it’s output in a file?

If so, is there any examples online so i can try understand it a bit better?

EDIT:

Simple Test case to pass in while compiling

import java.util.Iterator;

public class TestSet
{
public static void main(String[] args)
{
  try
  {
     System.out.print(   "[1]--constructor 1, size, isEmpty: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     if (s1.size() != 0)
        System.out.print("*** size? ***");
     if (!s1.isEmpty())
        System.out.print("*** isEmpty? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[2]--constructor 2, size, isEmpty: ");
     LinkedSet<String> s1 = new LinkedSet<String>( "alpha");
     if (s1.size() != 1)
        System.out.print("*** size? ***");
     if (s1.isEmpty())
        System.out.print("*** isEmpty? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[3]--contains: ");
     LinkedSet<String> s1 = new LinkedSet<String>("alpha");
     if (!s1.contains("alpha"))
        System.out.print("*** elt. not found ***");
     if (s1.contains("beta"))
        System.out.print("*** non-elt ``found'' ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[4]--add: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     if (s1.size() != 3)
        System.out.print("*** size? ***");
     if (!s1.contains("alpha") ||
        !s1.contains("beta") ||
        !s1.contains("gamma"))
        System.out.print("*** elt. not found ***");
     if (s1.contains("delta"))
        System.out.print("*** non-elt ``found'' ***");
     s1.add("beta");
     if (s1.size() != 3)
        System.out.print("*** size/duplicates? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[5]--remove: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     s1.remove("beta");
     s1.remove("alpha");
     s1.remove("gamma");
     if (s1.size() != 0)
        System.out.print("*** size? ***");
     if (s1.contains("alpha") ||
        s1.contains("beta") ||
        s1.contains("gamma"))
        System.out.print("*** non elt. ``found'' ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[6]--print: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("this");
     s1.add("is");
     s1.add("assignment");
     s1.add("four");
     s1.print();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[7]--addAll: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     LinkedSet<String> s2 = new LinkedSet<String>();
     s2.add("beta");
     s2.add("delta");
     s1.addAll(s2);
     if (!s1.contains("alpha") || ! s1.contains("beta") ||
        !s1.contains("gamma") || !s1.contains("delta"))
        System.out.print("*** elt. ``dropped'' ***");
     if (s1.size() != 4)
        System.out.print("*** size ? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }

  try
  {
     System.out.print(   "[8]--containsAll: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     LinkedSet<String> s2 = new LinkedSet<String>();
     s2.add("beta");
     s2.add("delta");
     if (s1.containsAll(s2))
        System.out.print("*** non-containment incorrect ***");
     LinkedSet<String> s3 = new LinkedSet<String>();
     s3.add("beta");
     s3.add("alpha");
     if (!s1.containsAll(s3))
        System.out.print("*** containment incorrect ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[9]--removeAll: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     s1.add("delta");
     LinkedSet<String> s2 = new LinkedSet<String>();
     s2.add("beta");
     s2.add("delta");
     s1.removeAll(s2);
     if (s1.contains("beta") || s1.contains("delta"))
        System.out.print("*** some  elts not removed? ***");
     if (!s1.contains("alpha") || !s1.contains("gamma"))
        System.out.print("*** wrong elts removed? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[10]--retainAll: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     s1.add("delta");
     LinkedSet<String> s2 = new LinkedSet<String>();
     s2.add("beta");
     s2.add("delta");
     s1.retainAll(s2);
     if (s1.contains("alpha") || s1.contains("gamma"))
        System.out.print("*** wrong elts retained? ***");
     if (!s1.contains("beta") || !s1.contains("delta"))
        System.out.print("*** wrong elts removed? ***");
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
  try
  {
     System.out.print(   "[11]--elements: ");
     LinkedSet<String> s1 = new LinkedSet<String>();
     s1.add("alpha");
     s1.add("beta");
     s1.add("gamma");
     s1.add("delta");
     Iterator<String> list = s1.elements();
     System.out.print("("+list.hasNext()+") ");
     if (list.hasNext())
        System.out.print(list.next()+"; ");
     System.out.print("("+list.hasNext()+")");
     if (list.hasNext())
        System.out.print(list.next()+"; ");
     System.out.print("("+list.hasNext()+")");
     if (list.hasNext())
        System.out.print(list.next()+"; ");
     System.out.print("("+list.hasNext()+")");
     if (list.hasNext())
        System.out.print(list.next()+"; ");
     System.out.print("("+list.hasNext()+")");
     if (list.hasNext())
        System.out.print(list.next()+"; ");   
     System.out.println();
  }
  catch(Exception e)
  {
     System.out.println("*** CRASH !!! ***");
  }
}
}

Answer 1

Ya you can……

1. Are you talking about the command line arguments, if yes then its possible..

Eg:

javac Test.java
enter code herejava Test Hello       // Hello is the Input

In Java this “Hello” input is sent to the main() method in it String[] array.

public static void main(String[] args)

So to access this Hello which you have passed as an Argument to the main() methods parameter, you need to do this..

 String s = args[0];

2. Now if you want to write this into a file internally from within the program do this.

 String s = args[0];
 File f = new File(d:\\vivek.txt);
 FileWriter fw = new FileWriter(f);
 BufferedWriter bw = new BufferedWriter(fw);

 bw.write(s);