I have this task. Input is
IP=192.23.30.40 message='Hello&derps.' user=destroyer
IP=192.23.30.41 message='Hello&yall.' user=destroyer
IP=192.23.30.40 message='Hello&hi.' user=destroyer
IP=192.23.30.42 message='Hello&Dudes.' user=destroyer
end
Output is:
child0:
192.23.33.40 => 1.
child1:
192.23.30.40 => 1.
destroyer:
192.23.30.42 => 2.
mother:
FE80:0000:0000:0000:0202:B3FF:FE1E:8329 => 1.
unknown:
192.23.155.40 => 1.
yetAnotherUsername:
192.23.50.40 => 2.
Basically I have to print every user with every IP and how many messages they have sent in format
username:
IP => count, IP => count… (last must be with dot in end)
The problem is I don't know how to added (row 27 in code trow exception, also don't know why) +1 to IP. And how to catch last value of last key.
package notReady;
import java.util.Scanner;
import java.util.TreeMap;
/**
* Created by Philip on 10-Jun-16.
*/
public class Problem09_02_UserLogs {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
TreeMap<String, TreeMap<String, Integer>> map = new TreeMap<>();
while (true) {
String in = scanner.nextLine();
if (in.equals("end")) {
break;
}
String[] input = in.split(" ");
String ip = input[0].replaceAll("IP=", "");
String user = input[2].replaceAll("user=", "");
if (!map.containsKey(user)) {
map.put(user, new TreeMap<>());
map.get(user).put(ip, 1);
}else {
Integer tempCount = (map.get(user).get(ip)) + 1;
map.get(user).put(ip, tempCount);
}
}
for (String person : map.keySet()) {
System.out.printf("%s: \n", person);
for (String ips : map.get(person).keySet()) {
System.out.printf("%s => %d.", ips, map.get(person).get(ips));
}
System.out.println();
}
}
}
This is next test, here everything is ok. input:
IP=FE80:0000:0000:0000:0202:B3FF:FE1E:8329 message='Hey&son' user=mother
IP=192.23.33.40 message='Hi&mom!' user=child0
IP=192.23.30.40 message='Hi&from&me&too' user=child1
IP=192.23.30.42 message='spam' user=destroyer
IP=192.23.30.42 message='spam' user=destroyer
IP=192.23.50.40 message='' user=yetAnotherUsername
IP=192.23.50.40 message='comment' user=yetAnotherUsername
IP=192.23.155.40 message='Hello.' user=unknown
end
Output:
destroyer:
192.23.30.40 => 2, 192.23.30.41 => 1, 192.23.30.42 => 1.
I'd have to guess (I won't count lines to see what is line 27) but it's probably this line: Integer tempCount = (map.get(user).get(ip)) + 1;. Have a look at your code: 3 lines above you put an empty treemap into map with the user being the key. Then you add a count for some ip. But if the next ip for that user is a different one you'll now try to get a value for a non-existant key from the map and add 1 to it.
Example:
user = "ThomasGo"
ip1 = "1.2.3.4"
After filling the maps you'd have something like this:
Map[key:"ThomasGo"->Map[key:"1.2.3.4"->1]]
Now the following call should succeed:
Integer tempCount = map.get("ThomasGo").get("1.2.3.4") + 1;
However, consider the next call to use a different ip, e.g. "2.2.2.2":
Integer tempCount = map.get("ThomasGo").get("2.2.2.2") + 1;
Since the inner map doesn't contain that ip map.get("ThomasGo").get("2.2.2.2") would return null. Next the system would try to unbox the null value in order to add 1 to it but that unboxing fails with a NullPointerException.
To fix that you'd have to check whether you actually get a count for the ip and if not just put 1 into the inner map.
Example:
Map<String, Integer> ipMap = map.get("ThomasGo");
//no map found for the username
if( ipMap == null ) {
//create a new inner map and put it into the outer map and keep the reference for further use
ipMap = new TreeMap<>();
map.put("ThomasGo", ipMap);
}
//check whether the ip is in the inner map
Integer ipCount = ipMap.get(ip);
if( ipCount == null) {
//no count in the map so just put 1
ipMap.put(ip, 1);
}
else {
//already a count in the map so overwrite it with count + 1
ipMap.put(ip, ipCount + 1);
}
And how to catch last value of last key.
That's actually easy, at least if I understand your requirement correctly: you don't need to. Just print each ip mapping and add a comma before all except the first (you can use a boolean flag for that) and after the loop instead of System.out.println(); you call System.out.println("."); which prints a dot and then a line break.