ICSE − Q & A

public class p 
{
    public static void main (String args [])
    {
       int i , a=0,j,b=0;     
       for (j=2;j<=100;j++)
       {          
       for(i=1;i<=j;i++)
        {
            if(j%i==0)  
            b=b+1;                     
    }
    if(b<=2)
     a=a+j;
}
System.out.print(a);
}
} 

program to find the sum of prime num , please correct my mistake in this !!!

//this is my program to reverse the case of characters i.e. lower case to upper case and uppercase to lowercase in a string what is the error plz tell me
import java.util.*;
public class tnaminatina
{
 public void check()
  {String a="",b="";
      Scanner sc=new Scanner(System.in);
    System.out.println("enter sentence");
   String s=sc.next();
   System.out.println("enter sentence");
   String g=sc.next(); 
   System.out.println("enter sentence");
   String d=sc.next();
   a=s.concat(g);
   b=a.concat(d);
   System.out.println(b);
   b=b.toUpperCase();
   System.out.println(b);
   b=b.trim();
   for(int i=0;i96&&b.charAt(i)<=122)
     c=(char)b.charAt(i)+32;
    else
    if(b.charAt(i)>64&&b.charAt(i)<=90)
     c=(char)b.charAt(i)-32;
    }
      System.out.println(b);
   }

 
  }

http://www.respaper.com/sarthakb/5348-pdf.html Question 8
its difficult giving lots of errors

Please provide answer and reason to your answer for the question in comments.