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HashSet.md

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Java HashSet

The important points about Java HashSet class are:
  • HashSet stores the elements by using a mechanism called hashing.
  • HashSet contains unique elements only.
  • HashSet allows null value.
  • HashSet class is non synchronized.
  • HashSet doesn't maintain the insertion order. Here, elements are inserted on the basis of their hashcode.
  • HashSet is the best approach for search operations.
  • The initial default capacity of HashSet is 16, and the load factor is 0.75.
importjava.util.*; classHashSet1{ publicstaticvoidmain(Stringargs[]){ //Creating HashSet and adding elements HashSet<String> set=newHashSet(); set.add("One"); set.add("Two"); set.add("Three"); set.add("Four"); set.add("Five"); Iterator<String> i=set.iterator(); while(i.hasNext()) { System.out.println(i.next()); } } }

Output

Five One Four Two Three 
importjava.util.*; classHashSet2{ publicstaticvoidmain(Stringargs[]){ //Creating HashSet and adding elements HashSet<String> set=newHashSet<String>(); set.add("Ravi"); set.add("Vijay"); set.add("Ravi"); set.add("Ajay"); //Traversing elements Iterator<String> itr=set.iterator(); while(itr.hasNext()){ System.out.println(itr.next()); } } }

Output

 Ajay Vijay Ravi 
importjava.util.*; classHashSet3{ publicstaticvoidmain(Stringargs[]){ HashSet<String> set=newHashSet<String>(); set.add("Ravi"); set.add("Vijay"); set.add("Arun"); set.add("Sumit"); System.out.println("An initial list of elements: "+set); //Removing specific element from HashSet set.remove("Ravi"); System.out.println("After invoking remove(object) method: "+set); HashSet<String> set1=newHashSet<String>(); set1.add("Ajay"); set1.add("Gaurav"); set.addAll(set1); System.out.println("Updated List: "+set); //Removing all the new elements from HashSet set.removeAll(set1); System.out.println("After invoking removeAll() method: "+set); //Removing elements on the basis of specified condition set.removeIf(str->str.contains("Vijay")); System.out.println("After invoking removeIf() method: "+set); //Removing all the elements available in the set set.clear(); System.out.println("After invoking clear() method: "+set); } }

Output

An initial list of elements: [Vijay, Ravi, Arun, Sumit] After invoking remove(object) method: [Vijay, Arun, Sumit] Updated List: [Vijay, Arun, Gaurav, Sumit, Ajay] After invoking removeAll() method: [Vijay, Arun, Sumit] After invoking removeIf() method: [Arun, Sumit] After invoking clear() method: []
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