Simple arrays in Java do not offer any method to update or replace an element. Nevertheless in ArrayList replace is pretty convenient to implement using the set method.
Method Header
arrayList.set(int index, dataType arrayListElement);
Parameters
The method takes 2 parameters.int index — The first one is the index of the element in ArrayList.
dataType arrayListElement — The second parameter is the data to be replaced at the index specified.
Return Type
The method returns the same ArrayList element that is just replaced.Example 1 - Replace element using the set() method
import java.util.ArrayList;
import java.util.List;
public class DriverClass {
public static void main(String[] args) {
List <String> weekDays = new ArrayList<>();
weekDays.add("Monday");
weekDays.add("Monday");
weekDays.add("Wednesday");
weekDays.add("Thursday");
weekDays.add("Friday");
weekDays.add("Saturday");
weekDays.add("Sunday");
System.out.println("Week Days (original) : " + weekDays + "\n");
String replacingText = "Tuesday";
String replacedText = weekDays.set(1, replacingText);
System.out.println("Replacing Text: " + replacingText);
System.out.println("Replaced Text: " + replacedText + "\n");
System.out.println("Week Days (updated) : " + weekDays);
}
}
Output
Week Days (original) : [Monday, Monday, Wednesday, Thursday, Friday, Saturday, Sunday]
Replacing Text: Tuesday
Replaced Text: Monday
Week Days (updated) : [Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday]
Explanation
In the snippet above, weekdays are added in an array list originally. However, Monday is added twice and Tuesday is missing. So, we replace it by Tuesday at the 1st index. This is done by using the set() method. Where index “1” and replacing text i-e “Tuesday” is passed. Later, we print out the ArrayList on the console to see the updates.Example 2
import java.util.ArrayList;
import java.util.List;
public class DriverClass1 {
public static void main(String[] args) {
List<Integer> dieRoll = new ArrayList<>();
dieRoll.add(0);
dieRoll.add(1);
dieRoll.add(2);
dieRoll.add(3);
dieRoll.add(4);
dieRoll.add(5);
System.out.println("Die Roll (original) : " + dieRoll + "\n");
dieRoll.set(0, 1);
dieRoll.set(1, 2);
dieRoll.set(2, 3);
dieRoll.set(3, 4);
dieRoll.set(4, 5);
dieRoll.set(5, 6);
System.out.println("Die Roll (updated) : " + dieRoll);
}
}
Output
Die Roll (original) : [0, 1, 2, 3, 4, 5]
Die Roll (updated) : [1, 2, 3, 4, 5, 6]
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