Very simple question, I think. How do I initialise an ArrayList called time.
Thanks.
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2use javadocs for such questions.duckduckgo.com/?q=!java+arraylistzengr– zengr2010-11-18 09:20:13 +00:00Commented Nov 18, 2010 at 9:20
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5 Answers
This depends on what you mean by initialize. To simply initialize the variable time with the value of a reference to a new ArrayList, you do
ArrayList<String> time = new ArrayList<String>();
(replace String with the type of the objects you want to store in the list.)
If you want to put stuff in the list, you could do
ArrayList<String> time = new ArrayList<String>();
time.add("hello");
time.add("there");
time.add("world");
You could also do
ArrayList<String> time = new ArrayList<String>(
Arrays.asList("hello", "there", "world"));
or by using an instance initializer
ArrayList<String> time = new ArrayList<String>() {{
add("hello");
add("there");
add("world");
}};
2 Comments
Sean Patrick Floyd
ArrayList<String> time = new ArrayList<String>(); ? Why not List<String> time = new ArrayList<String>(); ? (Variables should point to interfaces whenever possible)
aioobe
But how should I tell if this is possible in the OP's scenario? (Perhaps he has
time.ensureCapacity(1000) right below.) Why complicate things for such a beginner question?Arrays.asList allows you to build a List from a list of values.
You can then build your ArrayList by passing it the read-only list generated by Arrays.asList.
ArrayList time = new ArrayList(Arrays.asList("a", "b", "c"));
But if all you need is a List declared inline, just go with Arrays.asList alone.
List time = Arrays.asList("a", "b", "c");
1 Comment
sark9012
Before the constructor, I define attributes like private int day; private double hours;
ArrayList<String> time = ArrayList.class.newInstance();
1 Comment
Stephen C
Don't write code like this. Don't recommend other people write code like this. It is significantly slower than
new ... and you have to deal with 2 checked exceptions. (And since your code doesn't deal with the exceptions, it is technically wrong as well.)< 1.5 jdk
List time = new ArrayList();
gt or eq 1.5 jdk
List<T> time = new ArrayList<T>();
1 Comment
Sean Patrick Floyd
This is java 1.4 code. Please use
List<String> time = new ArrayList<String>(); insteadAlternative:
Using Google Collections, you could write:
import com.google.collect.Lists.*;
List<String> time = newArrayList();
You could even specify the initial contents of List as follows:
List<String> time = newArrayList("a", "b", "c");
