BufferedReader br1 = new BufferedReader(new InputStreamReader(System.in));

System.out.println("Enter the binary value:");
String s = br1.readLine();
System.out.println("Decimal value is :...

You need a update statement to update your table in oracle. See below for "Update" syntax:
UPDATE table
SET column = expression
WHERE predicates;

Also you google to find "update", you will find...