ducminhgd/java-basic

Java Basic Dev Log

Day 3

Problems

1. 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.
2. 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.

What I learn

• 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.

Day 2

Problems

From PoE:

• List of Fibonacci number to N.
• Count vowels in a string

What I learn

• 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.

Day 1

• Review syntax with Sum.SumToN, Sum.SumOddToN , and Sum.SumEvenToN.
• Remind me of inputting from Console.