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javaarraylistdouble
Robert Lu
Robert Lu

Reputation: 473

Java ArrayList of Doubles

Is there a way to define an ArrayList with the double type? I tried both 

ArrayList list = new ArrayList<Double>(1.38, 2.56, 4.3);

and 

ArrayList list = new ArrayList<double>(1.38, 2.56, 4.3);

The first code showed that the constructor ArrayList<Double>(double, double, double) is undefined and the second code shows that dimensions are required after double.

Upvotes: 19

Views: 206754

Answers (8)

Kaplan
Kaplan

Reputation: 31

1) "Unnecessarily complicated" is IMHO to create first an unmodifiable List before adding its elements to the ArrayList.

2) The solution matches exact the question: "Is there a way to define an ArrayList with the double type?"

double type:

double[] arr = new double[] {1.38, 2.56, 4.3};

ArrayList:

ArrayList<Double> list = DoubleStream.of( arr ).boxed().collect(
    Collectors.toCollection( new Supplier<ArrayList<Double>>() {
      public ArrayList<Double> get() {
        return( new ArrayList<Double>() );
      }
    } ) );

…and this creates the same compact and fast compilation as its Java 1.8 short-form:

ArrayList<Double> list = DoubleStream.of( arr ).boxed().collect(
    Collectors.toCollection( ArrayList::new ) );

Upvotes: 3

Kaplan
Kaplan

Reputation: 1

double[] arr = new double[] {1.38, 2.56, 4.3};

ArrayList<Double> list = DoubleStream.of( arr ).boxed().collect(
    Collectors.toCollection( new Supplier<ArrayList<Double>>() {
      public ArrayList<Double> get() {
        return( new ArrayList<Double>() );
      }
    } ) );

Upvotes: -1

Itay Maman
Itay Maman

Reputation: 30723

You can use Arrays.asList to get some list (not necessarily ArrayList) and then use addAll() to add it to an ArrayList:

new ArrayList<Double>().addAll(Arrays.asList(1.38L, 2.56L, 4.3L));

If you're using Java6 (or higher) you can also use the ArrayList constructor that takes another list:

new ArrayList<Double>(Arrays.asList(1.38L, 2.56L, 4.3L));

Upvotes: 2

Manish Doshi
Manish Doshi

Reputation: 1193

Try this: 

 List<Double> l1= new ArrayList<Double>();
 l1.add(1.38);
 l1.add(2.56);
 l1.add(4.3);

Upvotes: 2

Bohemian
Bohemian

Reputation: 424983

Try this:

List<Double> list = Arrays.asList(1.38, 2.56, 4.3);

which returns a fixed size list.

If you need an expandable list, pass this result to the ArrayList constructor:

List<Double> list = new ArrayList<>(Arrays.asList(1.38, 2.56, 4.3));

Upvotes: 31

Serhii Shevchyk
Serhii Shevchyk

Reputation: 39436

Using guava

Doubles.asList(1.2, 5.6, 10.1);

or immutable list

ImmutableList.of(1.2, 5.6, 10.1);

Upvotes: 2

x4nd3r
x4nd3r

Reputation: 900

You are encountering a problem because you cannot construct the ArrayList and populate it at the same time. You either need to create it and then manually populate it as such:

ArrayList list = new ArrayList<Double>();
list.add(1.38);
...

Or, alternatively if it is more convenient for you, you can populate the ArrayList from a primitive array containing your values. For example:

Double[] array = {1.38, 2.56, 4.3};
ArrayList<Double> list = new ArrayList<Double>(Arrays.asList(array));

Upvotes: 3

Rohan
Rohan

Reputation: 3078

Try this,

ArrayList<Double> numb= new ArrayList<Double>(Arrays.asList(1.38, 2.56, 4.3));

Upvotes: 4

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