value « Set « Java Collection Q&A

1. initialize java HashSet values by construction    stackoverflow.com

I need to create a Set with initial values.

    Set<String> h = new HashSet<String>();
    h.add("a");
    h.add("b");

2. maintaining TreeSet sort as object changes value    stackoverflow.com

I've got a object that defines a 'natural sort order' using Comparable<>. These are being stored in TreeSets. Other than removing and re-adding the object, is there another way to update the sort ...

3. What's the best way to validate the values of a Set in a unit test?    stackoverflow.com

Okay, often I'll have a method that returns a Set of some sort. The problem with unit testing such a method is that there is no guarantee an iteration over ...

4. Why Hashset dont take duplicate values?    stackoverflow.com

I have a doubt regarding hashset.Why Hashset dont take duplicate elements.I know it implements Set interface and places the values in hashtable.What i mean is what may be the code internally ...

5. HashSet retrieval of values    stackoverflow.com

public ArrayList resultSetToArrayList(ResultSet rs) throws SQLException {
    ResultSetMetaData md = rs.getMetaData();
    int columns = md.getColumnCount();
    ArrayList results = new ArrayList();

   ...

6. Get a Boolean value for whether an Object partially matches (Java)    stackoverflow.com

I think this is an easy question, if I could figure out search terms to describe it. It's similar to Java: Finding objects in collections except I just want a ...

7. Checking for String value in this Collections.synchronizedSet(new HashSet()) ?    coderanch.com

1) Yes, the advice is about iterating. What i thought is- they just want to give a idea- it may apply to other scenario- when using the contains method. 2) If we are just checking through contains method without using a synchronized block. So what is the use of making a synchronizing a set? (Just to make sure, only 1 thread ...

8. Adding duplicate values into HashSet    coderanch.com

9. sorting a hashset based on its value    coderanch.com

10. Employee with same values is being added two times in HashSet    coderanch.com

Hi , I have created a Employee overriding equals and hashCode . I am providing same values to the Employee Object , but please let me know why this is being added two times inside a HashSet (Even though they both are of same values ) Please see the code , public class Employee { private int age; private String name; ...

11. create TreeSet from HashSet and output the values to command window    java-forums.org

12. Getting duplicate values in hashset???    forums.oracle.com

Just a thought - because I really do not know! Can you use hashcode like that? Well as the method to be overridden is hashCode, not hashcode, you can do pretty much anything you like there. This is where the @Override annotation would have caught the typo. The contract of equals and hashCode is that if equals returns true, the two ...

13. How do I return a value in a HashSet?    forums.oracle.com

14. HashSet get() and contains() methods, by value or reference?    forums.oracle.com

System.out.println(myClassSet.contains(c1)); //true System.out.println(myClassSet.contains(c2)); //false System.out.println(myClassSet.contains(c3)); //false System.out.println(myClassSet.contains(c4)); //false ("MyClass" is a simple class that holds a String and an int). Is there any way I can get the set to select by value rather than reference for objects that aren't String? If so, is it possible that the value test could be customised, so that, for example, the above will ...