java inetaddress isreachable showing unexpected results

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Java

I am trying to ping 200s of IPs in a loop in every 10 seconds. So, this loop gets executed in every 10 seconds. I was using this code to ping the IPs

for (i = 0; i <= 200; i++ )
{
   ProcessBuilder processBuilder = new ProcessBuilder("ping", isWindows? "-n" : "-c", "1", *SOMEIP*);
   Process proc = processBuilder.start();

   int returnVal = proc.waitFor();
}

This is just the part of my code. I am creating separate thread for every ping because if 100 IPs are down, then it will take more than 300 seconds to ping each & every IP sequentially. So, created separate threads. But the problem was that whenever the loop gets executed, then the PCs CPU usage reaches to 90%, which is not good for a critical system. So I change the program to this one.

for (i = 0; i <= 200; i++ )
{
   InetAddress inet = InetAddress.getByName(*SOMEIP*);
   System.out.println(inet.isReachable(3000) ? "Host is reachable" : "Host is NOT reachable");

}

In the above code also, I am creating separate thread for each Ping because of the same problem. Now, here I am getting another problem. This code is giving unexpected result. The IPs which are pingable are also showing not reachable sometimes using above code. Why this is happening ?

Is there any other solution to this problem ?

Thanks