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Java Collection, ArrayList Exercises: Insert an element into the array list at the first position

Java Collection, ArrayList Exercises: Exercise-3 with Solution

Write a Java program to insert an element into the array list at the first position.

Pictorial Presentation:

Java Collection, ArrayList Exercises: Insert an element into the array list at the first position

Sample Solution:-

Java Code:

import java.util.*;
  public class Exercise3 {
  public static void main(String[] args) {
  // Creae a list and add some colors to the list
  List<String> list_Strings = new ArrayList<String>();
  list_Strings.add("Red");
  list_Strings.add("Green");
  list_Strings.add("Orange");
  list_Strings.add("White");
  list_Strings.add("Black");
  // Print the list
  System.out.println(list_Strings);
  // Now insert a color at the first and last position of the list
  list_Strings.add(0, "Pink");
  list_Strings.add(5, "Yellow");
  // Print the list
  System.out.println(list_Strings);
 }
}

Sample Output:

Note: Exercise3.java uses unchecked or unsafe operations.              
Note: Recompile with -Xlint:unchecked for details.                     
[Red, Green, Orange, White, Black]                                     
[Pink, Red, Green, Orange, White, Yellow, Black]

Flowchart:

Flowchart: Insert an element into the array list at the first position.

Java Code Editor:

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Java: Tips of the Day

getEnumMap

Converts to enum to Map where key is the name and value is Enum itself. 

public static <E extends Enum<E>> Map<String, E> getEnumMap(final Class<E> enumClass) {
    return Arrays.stream(enumClass.getEnumConstants())
            .collect(Collectors.toMap(Enum::name, Function.identity()));
}

Ref: https://bit.ly/3xXcFZt