What is the difference between String[] and List<String> in Apex?

By Yoonsoo Park | | 1 minutes
List vs Array

In Apex, arrays are collections of elements of the same type that are stored sequentially in memory. Each element in the array is accessed by an index, which starts from zero. Although Apex does not have a true “array” data type, the List data type in Apex is similar in behavior and can be used in much the same way as an array.

Example

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public classA {
  public string[] method1() {
    return new string[]{'string_value'};
  }

  public List<String> method2() {
    return new string[]{'string_value'};
  }

  public string[] method2() {
    return new List<String>{'string_value'};
  }

    public List<String> method2() {
    return new List<String>{'string_value'};
  }
}

These all method actually behave the same.

You can even do this

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List<String> example = new String[5];

myStrings[0] = 'the first'; 
myStrings.add('the second');

myStrings.set(2,'the third');
myStrings.add('the forth');

What is the difference then?

Array looking List cannot be used for nested arrays - arrays of arrays are not permitted in Apex. But! You can achieve this with List<Type>.

Example:

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List<List<Type>> nested = new List<List<Type>>();

Cheer! 🍺