From the Project Euler Problem 36: The decimal number, 585 = 10010010012 (binary), is palindromic in both bases. Find the sum of all numbers, less than one million, which are palindromic in base 10 and base 2. (Please note that the palindromic number, in either base, may not include leading zeros.) checked

Read More →## How to implement Up Navigation

In this example you can see how to implement the Up Navigation, i.e. the option to go back to a previous activity using the button in the upper left of the action bar. The previous activity can be a fixed activity or an activity determined at runtime.

Read More →## Circular primes

From the Project Euler Problem 35: The number, 197, is called a circular prime because all rotations of the digits: 197, 971, and 719, are themselves prime. There are thirteen such primes below 100: 2, 3, 5, 7, 11, 13, 17, 31, 37, 71, 73, 79, and 97. How many circular primes are there below […]

Read More →## Digit factorials

From the Project Euler Problem 34: 145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145. Find the sum of all numbers which are equal to the sum of the factorial of their digits. Note: as 1! = 1 and 2! = 2 are not sums […]

Read More →## Replacing a Fragment in a Tab Layout with an ActionBar

In the post Tab Layout in Android with ActionBar and Fragment the fragments can’t be replaced later, in this post I write the changes in order to replace the first fragment of the first tab with a third fragment using a button at runtime.

Read More →## Digit canceling fractions

From the Project Euler Problem 33: The fraction 49/98 is a curious fraction, as an inexperienced mathematician in attempting to simplify it may incorrectly believe that 49/98 = 4/8, which is correct, is obtained by cancelling the 9s. We shall consider fractions like, 30/50 = 3/5, to be trivial examples. There are exactly four non-trivial […]

Read More →## The services in Android

A service is a task running in the background to perform actions without a user interface and they are used to perform long running operations with a significant use of resources by avoiding delays in the user experience. The services belong to one or both of the following categories: started: the service is launched using […]

Read More →## Passing an object from an Activity to another

The method startActivity(Intent intent) of the class Activity allows you to call a second activity specified using the argument Intent. You can associate primitive data or primitive data array to the argument Intent and then the second Activity can access them, you can also pass objects of type String using methods of the class Bundle […]

Read More →## Pandigital products

From the Project Euler Problem 32: We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly once; for example, the 5-digit number, 15234, is 1 through 5 pandigital. The product 7254 is unusual, as the identity, 39 × 186 = 7254, containing multiplicand, multiplier, […]

Read More →## Javadoc in Eclipse and Android

In Eclipse launching javadoc from menu (Project -> generate javadoc…) if you get the errors: error: package android… does not exist error: cannot find symbol

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