What is wrong with this code.

package a$5.$disc;

import java.util.HashMap;

import java.util.HashSet;

import java.util.List;

import java.util.Map;

import java.util.Set;

import java.util.Vector;

public class DiscMain $\{$

public static void main$($String$[]$ args$)\{$

System.out.println$("$A$5$ Discussion $...")$;

Integer i$1=2000$;

Integer i$2=3005$;

String s$1=$ "This is not a number";

String s$2="4003"$;

Vector mylist $=$ new Vector$()$;

mylist.add$($ i$1)$;

mylist.add$($ i$2)$;

mylist.add$($ s$1)$;

mylist.add$($ s$2)$;

mylist.add$($ i$1)$;

mylist.add$($ i$2)$;

mylist.add$($ s$1)$;

mylist.add$($ s$2)$;

System.out.println$("$ List contains:"$)$;

for $($Object o : mylist$)$

System.out.println$(""+$ o $)$;

System.out.println$()$;

HashSet myset $=$ new HashSet$($ mylist $)$;

System.out.println$("$ Set contains:"$)$;

for $($Object o : myset$)$

System.out.println$(""+$ o $)$;

System.out.println$()$;

HashMap mymap $=$ new HashMap$()$;

mymap.put$($i$1,$ s$1)$;

mymap.put$($i$2,$ s$1)$;

mymap.put$($s$2,$ i$2)$;

mymap.put$($s$1,$ i$1)$;

Set keys $=$ mymap.keySet$()$;

System.out.println$("$ Map keys are:"$)$;

for $($ Object k : keys$)$

System.out.println$(""+$ k $)$;

System.out.println$()$;

System.out.println$("...$ done!"$)$;

$\}$

$\}$