Hi friend,

Code to solve the problem :

class JavaStringExample
{
public static void main(String[] args)
{
String str1 = args[0];
String str2 = args[1];
int str1Count=0;
int str2Count=0;
for(int i=0;i<str1.length();i++)
{
if(str1.charAt(i)=='a' || str1.charAt(i)=='A')
{

str1Count++;

}
}
for(int i=0;i<str2.length();i++)
{
if(str2.charAt(i)=='a' || str2.charAt(i)=='A')
{
str2Count++;
}
}
int totalCount = str1Count+str2Count;
String str11replace = str1.replace('a','@');
String str12replace = str11replace.replace('A','@');

String str21replace = str2.replace('a','@');
String str22replace = str21replace.replace('A','@');

System.out.println("The total number of occurrences of the character 'a' or 'A' : "+totalCount);
System.out.println("String 1 Replace : " + str12replace);
System.out.println("String 2 Replace : " + str22replace);
System.out.println("String 1 Uppercase : " + str12replace.toUpperCase());
System.out.println("String 2 Uppercase : " + str22replace.toUpperCase());
String strResult = str12replace.toUpperCase()+ str22replace.toUpperCase();
System.out.println("String Result : " + strResult);


}
}


Thanks