What values are the default variables initialized to

  • Numbers are initialized to 0 or 0.0;
  • char - \u0000;
  • boolean - false;
  • Objects (including String) - null.

Read also:


Comments

Post a Comment

Popular posts from this blog

Rocks and Diamonds

Image
In this post I want to tell about one simple programming task with solving in Java. Suppose we have two strings with latin symbols out of order. First string may have duplicates and that string we call Rocks. Second string have no duplicates and we call it Diamonds. Our task to find out how many Diamonds exist in Rocks. Every symbol in second string is diamond. If we want to use brute forse it will be not very effective. In that case we need to iterate full Rocks as many times as Diamonds exist in second string and we need to iterate the whole Rocks - from beginning to end. To become more efficient we will to execute two preparations - sort Rocks and Diamonds alphabetically. Now we have two sorted strings. Let begin iterate throught Diamonds and for every Diamond we iterate Rocks, but not the whole - when we found Diamond in Rock we increment our result counter, then take next Rock we check if it more then Diamond alphabetically. If it is then we take next Diamond because previous ...
Read more

ArrayList and LinkedList in Java, memory usage and speed

Image
How much extra memory is needed when calling ArrayList.add()? If there is enough space in the array to accommodate a new element, then no additional memory is required. Otherwise, a new array is created, 1.5 times larger than the existing one (this is true for JDK above 1.7, in earlier versions the size of the increase is different). How much extra memory is allocated when you call LinkedList.add()? One new instance of the nested Node class is created. How much memory to store one byte primitive in LinkedList? Each LinkedList element stores a link to the previous element, the next element, and a data link. private static class Node<E> { E item; Node<E> next; Node<E> prev; //... } For 32-bit systems, each link is 32 bits (4 bytes). The object (header) of the nested Node class itself takes 8 bytes. 4 + 4 + 4 + 8 = 20 bytes, and since the size of each object in Java is a multiple of 8, so we get 24 bytes. A byte primitive occupies 1 by...
Read more

Functional interfaces in Java

Image
A functional interface is an interface that defines only one abstract method. To precisely define an interface as functional, the @FunctionalInterface annotation has been added, working like the @Override principle. It will indicate the intent and prevent the second abstract method from being defined in the interface. An interface can include as many default methods as you want and still remain functional, because default methods are not abstract. Functional interfaces Function<T,R>, DoubleFunction<R>, IntFunction<R> and LongFunction<R> Function<T,R> is an interface that implements a function that receives an instance of the T class as input and returns an instance of the R class at the output. The default methods can be used to build call chains (compose, andThen). Function<String, Integer> toInteger = Integer::valueOf; Function<String, String> backToString = toInteger.andThen(String::valueOf); backToString.apply("123"); ...
Read more