The arrayList() is function of Kotlin ArrayList class, which is used to create a new ArrayList. ArrayList is mutable which means that we can modify the content of ArrayList.
Syntax:
fun arrayListOf()
It is used to create an empty new ArrayList.
fun arrayListOf(vararg elements: T)
It is used to create a new ArrayList with provided elements.
Example 1: Kotlin program to make new empty ArrayList.
fun main(args : Array<String>) { var arrList
= arrayListOf<String>() println(arrList.isEmpty())
println( "ArrayList : ${arrList}" )
} |
Output :
true ArrayList : []
Example 2: Kotlin program to make new ArrayList with String elements
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Python" ,
"JavaScript" )
println(arrList.isEmpty())
println( "ArrayList : ${arrList}" )
} |
Output :
false ArrayList : [Java, Python, JavaScript]
Example 3: Kotlin program to make new ArrayList with elements of any data type
fun main(args : Array<String>) { var arrList
= arrayListOf<Any>( 1 , 2 , 3 , "GeeksforGeeks" , 100.0 )
println(arrList.isEmpty())
println( "ArrayList : ${arrList}" )
} |
Output :
false ArrayList : [1, 2, 3, GeeksforGeeks, 100.0]
Property
ArrayList in kotlin has one property i.e. size. It returns the number of element in the ArrayList.
Example :
fun main(args : Array<String>) { var arrList = arrayListOf<String>();
println(arrList.size);
arrList.add( "GeeksforGeeks" );
println(arrList.size);
} |
Output :
0 1
Functions
The ArrayList class has the following functions:
add(element): This function is used to add the specified element to the ArrayList.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Python" );
println(arrList);
arrList.add( 0 , "Kotlin" );
println(arrList);
} |
Output :
[Java, Python] [Kotlin, Java, Python]
add(index, element): This function is used to add the element to the provided index of ArrayList.
fun main(args : Array<String>) { var arrList = arrayListOf<String>();
println(arrList);
arrList.add( "GeeksforGeeks" );
println(arrList);
} |
Output :
[] [GeeksforGeeks]
addAll(elementCollection): This function is used to add the specified collection of elements to the ArrayList.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" );
println(arrList);
arrList.addAll(listOf( "Python" , "JavaScript" ));
println(arrList);
} |
Output :
[Java, Kotlin] [Java, Kotlin, Python, JavaScript]
addAll(index, elementCollection): This function is used to add the specified collection of elements to the ArrayList at provided index.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" );
println(arrList);
arrList.addAll( 1 , listOf( "Python" , "JavaScript" ));
println(arrList);
} |
Output :
[Java, Kotlin] [Java, Python, JavaScript, Kotlin]
clear(): This function is used to remove all the elements from the ArrayList.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" );
println(arrList);
arrList.clear();
println(arrList);
} |
Output :
[Java, Kotlin] []
contains(element): This function is used to check whether an element exists in the ArrayList. It returns either true, if found, otherwise false
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" );
println(arrList.contains( "Kotlin" ));
} |
Output :
true
containsAll(elementCollection): This function is used to check whether a collection of elements exists in the ArrayList. It returns either true, if found, otherwise false
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Kotlin" , "Python" , "JavaScript" );
var checkList = listOf( "Python" , "Java" );
println(arrList.containsAll(checkList));
} |
Output :
true
get(index): This function is used to retrieve an element at the specified index from the ArrayList
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Kotlin" , "Python" , "JavaScript" );
println(arrList.get( 1 ));
} |
Output :
Kotlin
indexOf(element) This function returns the index of the first occurrence of the specified element in the ArrayList. If element is not present in the ArrayList, then it returns -1.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
println(arrList.indexOf( "Kotlin" ));
} |
Output :
1
lastIndexOf(element) This function returns the index of the last occurrence of the specified element in the ArrayList. If the element is not present in the ArrayList, then it returns -1.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
println(arrList.lastIndexOf( "Kotlin" ));
} |
Output :
3
remove(element) This function is used to remove a single instance of the specified element from the ArrayList. It returns true, if the element was present in the ArrayList and is removed, otherwise false.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
println(arrList.remove( "Kotlin" ));
println(arrList);
} |
Output :
true [Java, Python, Kotlin]
removeAll(elementCollection) This function is used to remove collection of element from the ArrayList. It returns true, if the element collection was removed, otherwise false.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
var delList = listOf( "Java" , "Kotlin" );
println(arrList.removeAll(delList));
println(arrList);
} |
Output :
true [Python]
removeAt(index): This function is used to remove an element by its position in the ArrayList. It returns true, if the element collection was removed, otherwise false.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
println(arrList.removeAt( 3 ));
println(arrList);
} |
Output :
Kotlin [Java, Kotlin, Python]
set(index, element) This function is used to add an element to the specified position in the ArrayList.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
arrList.add( 1 , "PHP" );
println(arrList);
} |
Output :
[Java, PHP, Kotlin, Python, Kotlin]
toArray() This function is used to convert the ArrayList to an array of type Array.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
var arr = arrList.toArray();
for (i in arr) {
println(i);
}
} |
Output :
Java Kotlin Python Kotlin
toString() This function is used to get the string representation of the ArrayList object.
fun main(args : Array<String>) { var arrList = arrayListOf<String>( "Java" , "Kotlin" ,
"Python" , "Kotlin" );
var arr = arrList.toString();
println(arr);
} |
Output :
[Java, Kotlin, Python, Kotlin]
isEmpty() This function returns true if the ArrayList is empty otherwise true
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Kotlin" , "Python" , "JavaScript" );
println(arrList.isEmpty());
} |
Output :
false
Traversal of the ArrayList
We can use the following way to traverse through an ArrayList. Using for loop (index wise)
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Python" , "JavaScript" , "Kotlin" );
for (index in 0 ..arrList.size- 1 ) {
println( "${index} => ${arrList.get(index)}" );
}
} |
Output :
0 => Java 1 => Python 2 => JavaScript 3 => Kotlin
Using for loop (element wise)
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Python" , "JavaScript" , "Kotlin" );
for (value in arrList) {
println(value);
}
} |
Output :
Java Python JavaScript Kotlin
Using while loop
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Python" , "JavaScript" , "Kotlin" );
var i = 0 ;
while (i < arrList.size) {
println(arrList.get(i)) i++;
}
} |
Output :
Java Python JavaScript Kotlin
Using Iterator
fun main(args : Array<String>) { var arrList = arrayListOf<String>(
"Java" , "Python" , "JavaScript" , "Kotlin" );
var itr = arrList.iterator();
while (itr.hasNext()) {
println(itr.next());
}
} |
Output :
Java Python JavaScript Kotlin