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Java ArrayList example

abstract 
Java class ArrayList(java.util.ArrayList) is a fast and easy to use class representing one-dimensional array. ArrayList is not synchronized i.e. using it in more that one thread may cause problems.
compatible 
  • Sun Java 1.5 or higher (because this example uses generics)
  • ArrayList class provides methods for basic array operations:

    • add( Object o ) - puts reference to object into ArrayList
    • get( int index ) - retrieves object reference from ArrayList index position
    • size() - returns ArrayList size
    • remove( int index ) - removes the element at the specified position in this list. Shifts any subsequent elements to the left and returns the element that was removed from the list.
    • indexOf( Object o) - finds the index in this list of the first occurrence of the specified element
    • clear() - removes all of the elements

    Following example ask user for his/her name, and suggests him/her a vacation place.

    ArrayList "myarr" is filled with resort names(add method). After user enters his name, we calculate residue of division of user's name length by myarr size -- operation result is a number from 0 to myarr.size()-1 -- which is suitable as array index.

    source code: Java
     
     
    import java.io.BufferedReader; 
    import java.io.IOException; 
    import java.io.InputStreamReader; 
    import java.util.ArrayList; 
     
    public class Ex01 { 
     
        public static void main(String[] args) throws IOException { 
     
            BufferedReader userInput = new BufferedReader 
                (new InputStreamReader(System.in));
     
            ArrayList<String> myArr = new ArrayList<String>();
            myArr.add("Italian Riviera");
            myArr.add("Jersey Shore");
            myArr.add("Puerto Rico");
            myArr.add("Los Cabos Corridor");
            myArr.add("Lubmin");
            myArr.add("Coney Island");
            myArr.add("Karlovy Vary");
            myArr.add("Bourbon-l'Archambault");
            myArr.add("Walt Disney World Resort");
            myArr.add("Barbados");
     
            System.out.println("Stupid Vacation Resort Adviser");
            System.out.println("Enter your name:");
            String name = userInput.readLine();
            Integer nameLength = name.length();
            if (nameLength == 0) 
            { 
                System.out.println("empty name entered");
                return;
            } 
     
            Integer vacationIndex = nameLength % myArr.size();
     
            System.out.println("\nYour name is "+name+", its length is " + 
                            nameLength + " characters,\n" +
                            "that's why we suggest you to go to " 
                            + myArr.get(vacationIndex));
        } 
    } 
     
    warning 
  • ArrayList stores only object references. That's why, it's impossible to use primitive data types like double or int. Use wrapper class (like Integer or Double) instead.
  • For multi-theaded(synchronized) array class use Vector (java.lang.Vector)
  • tested 
  • JDK 1.5
  •  


     
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