Binary Search vs Contains Performance in Java List

There are two ways to search an element in a List class, by using contains() method or by using Collections.binarySearch() method. There are two versions of binarySearch() method, one which takes a List and Comparator and other which takes a List and Comparable. This method searches the specified list for the specified object using the binary search algorithm. The list must be sorted into ascending order according to the natural ordering of its elements (as by the sort(List) method) prior to making this call. If List is not sorted, then results are undefined. If the List contains multiple elements equal to the specified object, there is no guarantee which one will be returned. This method runs in log(n) time for a "random access" list (which provides near-constant-time positional access). If the specified list does not implement the RandomAccess interface and is large, this method will do an iterator-based binary search that performs O(n) link traversals and O(log n) element comparisons. In the end this method returns the index of the search key, if it is contained in the list; otherwise, (-(insertion point) - 1). The insertion point is defined as the point at which the key would be inserted into the list: the index of the first element greater than the key, or list.size() if all elements in the list are less than the specified key. This means that return value will be >= 0 if and only if the key is found. Since common implementation of List interface e.g. ArrayList, Vector, CopyOnWriteArrayList and Stack implements RandomAccess interface, they can be used for performing binary search, but there are other implementations like LinkedList, which doesn't implement java.util.RandomAccess, hence not suitable for binary search operation. Since binary search can only be performed in sorted list, you also need to sort your collection before doing search, which may potentially impact performance, especially if your List is big and not in sorted order already.

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How to Format and Display Number to Currency in Java - Example Tutorial

Displaying financial amount in respective currency is common requirement in Java based E-commerce applications. For example if you are selling products on-line globally, you will show price of product in their local currency rather than USD or some other currency. Storing price in every currency is not a good option because of maintenance, and more realistically fluctuation in exchange rates. That's why many of these application prefer stores price of books, electronic goods or whatever product they are selling in USD, and responsibility of converting that price to local currency and displaying is left to client side code. If your client is Java based client e.g. Swing GUI , Java FX client, or a JSP web page, you can use java.text.NumberFormat class to format currency in Java. NumberFormat class allows you to display price in multiple currency depending upon Locale supported by your Java version. All you need to do is to get correct Currency Instance based upon Locale, for example to display amount in US dollar, call NumberFormat.getCurrencyInstance() method with Locale as Locale.US, similarly to display currency as UK pound sterling, pass Locale.UK and for displaying money in Japanese Yen, pass Locale.JAPAN. Once you get the correct instance of currency formatter, all you need to do is call their format() method by passing your number. We will see an example of converting one currency to other and displaying amount in multiple currency in Java. It's actually very much similar to formatting date in Java, so if you are familiar to that part, it would be easy to format currency as well.

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How clone method works in Java

clone is a tricky method from java.lang.Object class, which is used to create copy of an Object in Java. Intention of clone() method is simple, to provide a cloning mechanism, but some how it's implementation became tricky and has been widely criticized from long time. Anyway, we will not go to classic debate of clone in Java, at-least for now; instead, we will try to learn how clone method works in Java. To be fair, understating cloning mechanism in Java is not easy and even experienced Java programmer fail to explain how cloning of mutable object works, or difference between deep copy and shallow copy in Java. In this three part article, we will first see working of clone method in Java, and in second part we will learn how to override clone method in Java, and finally we will discuss deep copy vs shallow copy mechanism. The reason I chose to make this a three part article, is to keep focus on one thing at a time. Since clone() itself is confusing enough, it's best to understand concept one by one. In this post, we will learn what is clone method, what it does and How clone method works in Java. By the way, clone() is one of the few fundamental methods defined by objects, others being equals, hashcode(), toString() along with wait and notify methods.

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JSTL forTokens Tag Example - Split String in JSP

JSTL forTokens tag is another tag in core JSTL library to support Iteration or looping. It effectively complements, more useful <c:forEach> tag, by allowing you to iterate over comma separated or any delimited String. You can use this tag to split string in JSP and can operate on them individually. forTokens tag has similar attribute like forEach JSTL tag except one more attribute called delims, which specifies delimiter. For example to iterate over colon separated String "abc:cde:fgh:ijk", delims=":". By the way, forTokens tag also accept multiple delimiter, which means, you can split a big string into token based upon multiple delimiter e.g. colon(:) and pipe (|), This will be more clear, when we will see examples of JSTL forTokens tag in JSP. Rest of attribute e.g. items, var, varStatus, begin, end and step are same, as they are in case of <c:forEach> tag. For quick review, items specify String which needs to be split-ed in token and var hold current String.

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How to parse String to Float in Java | Convert Float to String in Java - 3 Examples

float and double are two data type which is used to store floating point values in Java and we often need to convert String to float in Java and sometime even a Float object or float primitive to String. One thing, which is worth remembering about floating point numbers in Java is that they are approximate values, a float value 100.1f may hold actual value as 100.099998, which will be clear, when we seen examples of converting float to String and vice-versa. By the way, It's easy to parse String to float and vice-versa, as rich Java API provides several ways of doing it. If you already familiar with converting String to int or may be String to double in Java, then you can extend same techniques and method to parse float String values. key methods like valueOf() and parseInt(), which is used to parse String to float are overloaded for most primitive data types. If you are particularly interested on rounding of float values, you can use RoundingMode and BigDecimal class, as float and double are always approximate values and comparing two float variable of same values may not always return true, that's why it's advised, not to use float for monetary calculation. In this Java tutorial, we will first see examples of parsing String to float in Java and later converting float to String objects. Remember, we will use float and Float, a wrapper class corresponding to float primitive, interchangeably because by using Java 1.5 autoboxing feature, they are automatically converted to each other, without any Java code. For those, who are still in Java 1.4 or lower version, then can use Float.floatValue() to convert Float wrapper object to float primitive.

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