One line initialization of an ArrayList object in Java

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It is very tedious and lengthy to create an ArrayList and add elements to it. 

for example:

ArrayList<String> student = new ArrayList<String>();
places.add("john");
places.add("james");
places.add("jill");

Is there a better way to do it?

Apr 13, 2018 in Java by Daisy
• 8,040 points
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2 answers to this question.

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0 votes

Java 9 has some new Factory methods for collections:

For List object - List.of() method 
List<String> places=new ArrayList<>(List.of( "john","james","jill");

These factory methods of Java 9 has many advantages:

  1. Space Efficiency
  2. Immutability
  3. Thread Safe
answered Apr 13, 2018 by parth295
• 4,600 points
0 votes

In Java 8 or earlier:

List<String> string = Arrays.asList("foo", "bar", "baz");

This will give you a List backed by the array, so it cannot change length.
But you can call List.set, so it's still mutable.


In Java 9:

List<String> string = List.of("foo", "bar", "baz");

This will give you an immutable List, so it cannot be changed.
Which is what you want in most cases where you're prepopulating it.

answered Jul 26, 2018 by samarth295
• 2,190 points

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