How to make a deep copy of Java ArrayList

java arraylist deep-copy
Pnutz picture Pnutz · Aug 12, 2011 · Viewed 159.2k times · Source

Possible Duplicate:
How to clone ArrayList and also clone its contents?

trying to make a copy of an ArrayList. The underlying object is simple containing on Strings, ints, BigDecimals, Dates and DateTime object. How can I ensure that the modifications made to new ArrayList are not reflected in the old ArrayList?

Person morts = new Person("whateva");

List<Person> oldList = new ArrayList<Person>();
oldList.add(morts);
oldList.get(0).setName("Mortimer");

List<Person> newList = new ArrayList<Person>();
newList.addAll(oldList);

newList.get(0).setName("Rupert");

System.out.println("oldName : " + oldList.get(0).getName());
System.out.println("newName : " + newList.get(0).getName());

Cheers, P

Answer

Serabe picture Serabe · Aug 12, 2011

Cloning the objects before adding them. For example, instead of newList.addAll(oldList);

for(Person p : oldList) {
    newList.add(p.clone());
}

Assuming clone is correctly overriden inPerson.

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