class - I'm having problems understanding how this Java works with the arguments I'm feeding it -

-

the issue i'm having understanding code when running command: java driver 1000000 returning: sum(1000000) = 1784293664

and no matter how long try @ cant understand why , how code doing im wondering if can provide in understanding code number?

class sum {   private int sum;    public int get() {     return sum;   }    public void set(int sum) {     this.sum = sum;   } }  class summation implements runnable {   private int upper;   private sum sumvalue;    public summation(int upper, sum sumvalue) {     this.upper = upper;     this.sumvalue = sumvalue;   }    public void run() {     int sum = 0;      (int = 0; <= upper; i++)       sum += i;      sumvalue.set(sum);   } }  public class driver {   public static void main(string[] args) {     if (args.length != 1) {       system.err.println("usage driver <integer>");       system.exit(0);     }      if (integer.parseint(args[0]) < 0) {       system.err.println(args[0] + " must >= 0");       system.exit(0);     }      // create shared object     sum sumobject = new sum();     int upper = integer.parseint(args[0]);      thread worker = new thread(new summation(upper, sumobject));     worker.start();      try {       worker.join();     } catch (interruptedexception ie) { }     system.out.println("sum(" + upper + ") = " + sumobject.get());   } }

thanks in advance

andrew

summing numbers 1 through 1 million:

(1 + 1000000) * 1000000 / 2 = 500000500000

this causes overflow in int you're using hold sum. result is:

500000500000 (mod 2^32) = 1784293664

use long store sum; has maximum value of 9223372036854775807 , can hold sum.


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more

erlang - Saving a digraph to mnesia is hindered because of its side-effects -

-
updated the digraph library in erlang implements data type side-effectful. each operation on data type saves new state in ets table -- instead of returning altered version of itself, more common in functional languages. the problem usage perspective, impedes effort store or pass around state in convenient way requiring me first "collect" state before can start juggle around. the closest solution have seen far serializer/deserializer , these have drawback tied current structure of digraphs instead of operating on abstract type -- prevents future proof solution. update pascal pointed out serializer utilizes interface of digraph, , hence eliminates drawback mentioned above. better, albeit still inconvenient, see no better alternative. what recommendation on how store digraphs? should go different data type altogether? thanks. i not sure understand concern. fact digraph stored in ets transparent in user interface, might want chnge either exchange digr...
Read more