Create Java Random from the size of the List -

Create Java Random from the size of the List -

i have created method randomize list:

public <t> list<t> randomize(list<t> list) { linkedlist<t> randomizedlist = new linkedlist<>(); random random = new random(list.size()); (int = random.nextint(); < list.size(); i++) { randomizedlist.add(list.get(i)); } homecoming randomizedlist; }

the list passing method contains e.g. 5 elements. when creating random random = new random(list.size()); expect when phone call random.nextint() homecoming me random integer index of list element.

but when phone call random.nextint(); instead of returning number interval [0, 4] (which expect returned) returns me value of e.g.: -349120689. gives me java.lang.indexoutofboundsexception: index: -349120689, size: 5.

why happening , how solve this?

new random(list.size()); sets seed of random number generator list.size(); suggest changing new random() (which give seed based on current time of system). preferably though, you'd want reuse same random object @ times.

random.nextint(); here you'd want set random.nextint(list.size()); give number 0 list.size() - 1.

even above changes, code give sublist of list starting @ random index , going until end. utilize collections.shuffle(list) instead.

to real shuffling, need "remember" elements have inserted or not. in pseudo-code, following:

copy original list new one, let's phone call "orig" create new, empty, list, let's phone call "result" as long orig list has elements, element @ random index , add together result list. remove chosen element orig list. return result list.

java list random