Question

import java.io.*;
import java.lang.*;

public class Propogate1
{

String reverse(String name)
{
if(name.length()==0)
    throw IOException("name");

String reverseStr="";
for(int i=name.length()-1;i>0;--i)
{
  reverseStr+=name.charAt(i);

}
return reverseStr;
}

public static void main(String[] args)throws IOException
{
String name;
try
{
        Propogate1 p=new Propogate1();
    p.reverse("java");

}
finally
{
System.out.println("done");
}

}

}

I have to create a class propogate and main method which will call reverse(). In that if the name.length is null, it will throw an exception. If it is not null it will reverse the string. Pls help me

Answer 1

May be this is what you need.

package reversestring;

// import java.io.* is not needed here. 
// And if you want to import anything,
// prefer specific imports instead and not entire package.

// java.lang.* is auto-imported. You needn't import it explicitly.      

public class Propogate {
  // There's no reason this method should be an object method. Make it static.
  public static String reverse(String name) {
    if (name == null || name.length() == 0) {
      // RuntimeExceptions are preferred for this kind of situations.
      // Checked exception would be inappropriate here.
      // Also, the error message should describe the kind of exception
      // occured.
      throw new RuntimeException("Empty name!");
    }
    // Idiomatic method of string reversal:
    return new StringBuilder(name).reverse().toString();
  }

  public static void main(String[] args) {
    String name;
    try {
      name = Propogate.reverse("java");
      System.out.println("Reversed string: " + name);
    } catch (RuntimeException rx) {
      System.err.println(rx.getMessage());
    } finally {
      // I don't get the point of `finally` here. Control will reach this
      // point irrespective of whether string reversal succeeded or failed.
      // Can you explain what do you mean by "done" below?
      System.out.println("done");
    }
  }
}

/*

Output:-

Reversed string: avaj

done

*/