performance - Java: Reusing vs Reallocating reference to container object? -

tl;dr: in java, better, reusing of container object or creating object every time , let garbage collector work

i dealing huge amount of data in java have following type of code structure:-

version1:

for(...){//outer loop    hashset<integer> test = new hashset<>(); //some container    for(...){       //inner loop working on above container data structure    }    //more operation on container defined above }//outer loop ends 

here allocated new memory every time in loop , operations in inner/outer loop before allocating empty memory again.

now concerned memory leaks in java. know java has garbage collector instead of relying on should modify code follows:-

version2:

hashset<integer> test = null; for(...){//outer loop    if(test == null){       test = new hashset<>(); //some container    }else{       test.clear()    }    for(...){       //inner loop working on above container data structure    }    //more operation on container defined above }//outer loop ends 

i have 3 questions:-

1. which perform better, or there no definitive answer.
2. will second version have more time complexity? in other other words clear() function o(1) of o(n) in complexity. didn't in javadocs.
3. this pattern quite common, version more recommended one?

to opinion it's better use first approach. note hashset.clear never shrinks size of hash-table. if first iteration of outer loop adds many elements set, hash-table become quite big, on subsequent iterations if less space necessary if won't shrinked.

also first version makes further refactoring easier: may later want put whole inner loop separate method. using first version can move hashset.

finally note garbage-collection it's easier manage short-lived objects. if hashset long-lived, may moved old generation , removed during full gc.