Java Basic Dev Log

Day 3

From Bing: Write a Java program that reads an integer between 0 and 1000 and adds all the digits in the integer. For example, if an integer is 932, the sum of all its digits is 14.
From PoE: Write a program that takes a string as input and checks if the string is a palindrome. A palindrome is a word, phrase, number, or other sequence of characters that reads the same backward as forward.

Remind me from using maven to build source code
To run a main function of a class java -classpath .\target\classes\ dev.ducminhgd.numeric.Sum.

From PoE:

Remind me of recursive function.
java.util.List is an interface, so you cannot use List<Integer> l = new List<Integer>();. Use new ArrayList<Integer>() instead.
java.util.Array is a fixed size type, all elements must be the same type. Data is located on continuous memory zone.
java.util.ArrayList is a dynamic size type. It can contain both primitive type or Object type. If T is an Object Type, ArrayList can contain T's inheritances.
Integer is a wrapper class of int, and provides methods that working with that int value.
- Default value of an int variable is 0, and default value of Integer is null.
- Integer can be contained in a Java Collection type, but int.
Use "aeiou".indexOf(c)!=-1 to check if c is one of the five vowels or not.