How to replace line breaks , New lines from String in Java.- Windows, Mac or Linux

We often need to replace line terminator characters, also known as line breaks e.g. new line \n and carriage return \r with different characters. One of the common case is to replace all line breaks with empty space in order to concatenate multiple lines into one long line of String. In order to replace line breaks, you must know line terminator or new line characters for that platform. For example, In Windows operating system e.g. Windows 7 and 8, lines are terminated by \n\r also known as CR+LF, while in Unix environment e.g. Linux or Solaris line terminator is \n, known as line feed LF. You can also get line terminator pragmatically by using Java system property line.terminator. Now question is, How can you replace all line breaks from a string in Java in such a way that will work on both Windows and Linux (i.e. no OS specific problems of carriage return/line feed/new line etc.)? Well, You can use System.getProperty("line.terminator") to get the line break in any OS and by using String replace() method, you can replace all line breaks with any character e.g. white space. replace() method from java.lang.String class also supports regular expressions, which makes it even more powerful. In next section we will learn how to replace all line breaks from Java String by following a simple code example. By the way, if you are removing line breaks from String then don't forget to store result of replace() method into same variable. Since String is immutable in Java, any change on it will always produce a new String, if you assume that call to replace() will change the original string then it's not going to happen. For example, in below code original String text will remain unchanged, even after calling replace() method.

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3 ways to Find First Non Repeated Character in a String - Java Programming Problem

Write a Java program to find first non repeated character in a String is a common question on coding tests. Since String is a popular topic in various programming interviews, It's better to prepare well with some well-known questions like reversing String using recursion, or checking if a String is palindrome or not. This question is also in the same league. Before jumping into solution, let's first understand this question. You need to write a function, which will accept a String and return first non-repeated character, for example in world "hello" , except 'l' all are non-repeated, but 'h' is the first non-repeated character. Similarly in word "swiss" 'w' is the first non-repeated character. One way to solve this problem is creating a table to store count of each character, and then picking the first entry which is not repeated. Key thing to remember is order, your code must return first non-repeated letter. By the way, In this article, we will see 3 examples to find first non repeated character from a String. Our first solution uses LinkedHashMap to store character count, since LinkedHashMap maintains insertion order and we are inserting character in the order they appear in String, once we scanned String, we just need to iterate through LinkedHashMap and choose the entry with value 1. Yes, this solution require one LinkedHashMap and two for loops. Our second solution is a trade-off between time and space, to find first non repeated character in one pass. This time, we have used one Set and one List to keep repeating and non-repeating character separately. Once we finish scanning through String, which is O(n), we can get the magic character by accessing List which is O(1) operator. Since List is an ordered collection get(0) returns first element. Our third solution is also similar, but this time we have used HashMap instead of LinkedHashMap and we loop through String again to find first non-repeated character. In next section, we will the code example and unit test for this programming question. You can also see my list of String interview Questions for more of such problems and questions from Java programming language.

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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 Check if a Number is Binary in Java - Programming Problem

Today we will take a look on another simple programming exercise, write a program to check if a number is binary in Java. A number is said to be binary if it only contains either 0 or 1, for example 1010 is binary number but 1234 is not. You can not any library method to solve this problem, you need to write a function to check if given number is binary, you can use basic constructs of Java programming language e.g. operators, keywords, control statements etc. If you are a regular reader of Javarevisited, then you know that I love to share simple programming problems here, because they serve two purposes, first they help beginners to apply their basic knowledge to do something which looks challenging at first, and second they serve as good coding questions to differentiate candidates on Java interviews between who can program and who can not. FizzBuzz is one of such problems but their are lot many, e.g. Prime numbers, Fibonacci series or factorial. But if you truly want to test your candidate then you need to give them some questions which are not so popular. If a candidate can apply his programming knowledge to a problem he is seeing first time, he is probably going to perform better than the candidate who has already seen the problem. That's why I was always looking at programming problems, which are not difficult to solve but has some element of freshness and not so common. This problem of checking whether a number is binary or not is not very different from converting a decimal to binary, but it will pose challenge for those programmers who can't code. By the way, if you are looking for simple programming problems, you can check my list of Top 30 programming interview questions, their I have shared questions from several popular topics including String, Array, Data Structure and Logic.

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Why use Underscore in Numbers from Java SE 7 - Underscore in Numeric Literals

JDK 1.7 release had introduced several useful features, despite most of them being syntactic sugar, there use can greatly improve readability and code quality. One of such feature is introduction of underscore in numeric literals. From Java 7 onwards you can write a long digit e.g. 10000000000 to a more readable 10_000_000_000 in your Java source code. One of the most important reason of using underscore in numeric literal is avoiding subtle mistakes which is hard to figure out by looking at code. It's hard to notice a missing zero or extra zero between 10000000000 and 1000000000, than 10_000_000_000 and 1_000_000_000. So if you are dealing with big numbers in Java source code, use underscore in numbers to improve readability. By the way, there are rules to use underscore in numeric literals, as they are also a valid character in identifier, you can only use them in between digits, precisely neither at the start of numeric literal nor at the end of numeric literals. In next couple of section, we will learn how underscore in numeric literal is implemented and rules to use them in numerical literals.

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Covariant Method Overriding of Java 5 - Coding Best Practices

Sometime knowledge of a specific Java feature can improve code quality, Covariant method overriding is one of such feature. Covariant method overriding was introduced in Java 5, but it seems it lost between other more powerful features of that release. Surprisingly not many Java programmer knows about Covariant overriding, including myself, until I read, one of the best Java book on Collection framework, Java Generics and Collection. Covariant method overriding helps to remove type casting on client side, by allowing you to return subtype of actually return type of overridden method. Covariant overriding can be really useful, while overriding methods which returns object e.g. clone() method. Since clone() return object every client needs to cast on to appropriate subclass, not any more. By using Java 5 covariant overriding, we can directly return subtype instead of object, as we will seen in examples of this article. This feature is not a star feature like Generics or Enum, but it's definitely something worth knowing, given overriding methods are integral part of Java programming. I have discussed a bit about this feature earlier in difference between overriding and overloading article, and here I will show couple of more examples to justify it's usage.

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Why Static Code Analysis is Important?

From last few years, Software code quality and security has went from being a �nice to have� to a necessity, and many organizations, including investment banks are making it mandatory to pass static code analysis test, penetration testing and security testing before you deploy your code in production. Static analysis tools like findbugs and fortify are getting popular every passing day and more and more companies are making fortify scan mandatory for all new development. For those unaware of what static code analysis is, static code analysis is about analysing your source code without executing them to find potential vulnerabilities, bugs and security threats. Static code analyser looks for patterns, defined to them as rules, which can cause those security vulnerability or other code quality problems, necessary for production quality code. But like every other technology, static analysis has it�s set of advantages and disadvantages, which is also best way to judge any technology. Static code analyser are not a new thing, and they are here from long time, but as a senior Java developer or Team lead, you have responsibility to set-up process like automated code analysis, continuous integration, automation testing to keep your project in healthy state and promote best development practices in your team. In my opinion, unit testing, code review and static code analysis makes a nice combo, along with continuous integration. In this article, we will learn some pros and cons of static code analysis, to let you decide, whether static analysis is important or not. I am already convinced with pros, and we are using fortify scanning in all our projects, and have seen benefits of that, but its not all good, its also time consuming. When your tool alert you with false positive, you start taking them lightly and then it become habit to treat everything as false positive, which eventually take away all benefits of static code analysis. You need to be discipline enough, not to fall on that trap.

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10 Equals and HashCode Interview Questions in Java

Equals and HashCode methods in Java are two fundamental methods from java.lang.Object class, which is used to compare equality of objects, primarily inside hash based collections such as Hashtable and HashMap. Both equals() and hashCode() are defined in java.lang.Object class and there default implementation is based upon Object information e.g. default equals() method return true, if two objects are exactly same i.e. they are pointing to same memory address, while default implementation of hashcode method return int and implemented as native method. Similar default implementation of toString() method, returns type of class, followed by memory address in hex String. It's advised to override these method, based upon logical and business rules e.g. String overrides equals to check equality of two String based upon content, we have also seen and example implementation of equals() and hashCode for custom classes. Because of there usefulness and usage, they are also very popular in various level of Java Interviews, and In this tutorial, I am going to shared some of the really interesting questions from equals() and hashCode() method in Java. This question not only test your concept on both method, but also gives an opportunity to explore them more.

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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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