I'm starting in java language, with netbeans. I do some exercises, I just can not understand how the next cycle works:
if (num<=1){
return false;
}else{
int prueba;
int contador=0;
prueba=(int)Math.sqrt(num);
for (;prueba>1;prueba--){
if (num%prueba==0){
contador+=1;
}
}
return contador < 1;
}
prueba has dividers. Classic for has 3 "sections":
definition and initialization of variables;
an expression that returns boolean that indicates whether to continue iterating;
actions to be taken at the end of each loop.
In your case
for (;prueba>1;prueba--){
there is no definition or initialization of variables, variables defined before are used;
will iterate as long as% co_of% is greater than 1;
after each iteration, 1 will be subtracted from prueba (so at some point prueba will end up being prueba or less).
The condition
if (num%prueba==0){
Check if the modulo operation 1 (the "remainder" of the division) returns 0. If so, % is a divisor of prueba .
Finally,
prueba=(int)Math.sqrt(num);
If num has some divisor, some of these must be between prueba and square root of 1 in fact the exact half of the divisors, except in the case of perfect squares. When starting prueba with this value, if there is a divisor the value of prueba will be contador or greater, if it does not exist it will be 1 .