You have given a String and a subString or a character and you need to find out whether given String contains the given character or substring, how would you do that? Well, there are three main ways to search String in Java, the contains() method, the indexOf() method and the lastIndexOf() method, all from java.lang.String class. First method, contains() accepts a CharSequence, superclass of String and return true if that CharSequence appear on the String you have called. The indexOf() and lastIndexOf() are similar method and both return the index (zero based) from where the given subString or character appear in the String you have called. Only difference between indexOf() and lastIndexOf() is that if given substring appear multiple time then they will return difference index, otherwise both will return the same index. Similarly if given sub-string is not present in the String, both will return -1 and contains() will return false.
How to make Immutable class in Java? Mutable vs Immutable Objects
How I make immutable objects in Java? I've always thought that all objects are immutable, because if you change the content of an String example, it will always create you an new String object and point to that. However later I found that String is a special class and its specially designed as an Immutable class because its often cached. Obviously you cannot cache anything which is not constant and that make sense why String is Immutable in Java. But this encouraged me to learn more about Mutable and Immutable class in Java and how to create a custom Immutable class in Java.
Difference between StringTokenizer and Split method in Java? Example
There are multiple ways to split a String in Java, but two of the most common ways are by using StringTokenizer and the split method of String class. You can use either one of them, but when to use which one? This short article will give you some details about StringTokenizer and Split method in Java to decide which one to use.
1) The StringTokenizer is legacy, Prefer split() as more chances of its performance getting improved as happens in Java 7.
2) The StringTokenizer doesn't support regular expression, while spilt() does. However, you need to be careful, because every time you call split, it creates a new Pattern object and compiles expression into a pattern. This means if you are using the same pattern with different input, then consider using Pattern.split() method, because compiling a pattern takes more time later to check whether a given string matches a pattern or not.
1) The StringTokenizer is legacy, Prefer split() as more chances of its performance getting improved as happens in Java 7.
2) The StringTokenizer doesn't support regular expression, while spilt() does. However, you need to be careful, because every time you call split, it creates a new Pattern object and compiles expression into a pattern. This means if you are using the same pattern with different input, then consider using Pattern.split() method, because compiling a pattern takes more time later to check whether a given string matches a pattern or not.
5 ways to Compare String Objects in Java - Example Tutorial
here are many ways to compare String in Java e.g. you can use equals() and equalsIgnoreCase() for equality check and compare() and compareTo() for ordering comparison. You can even use the equality operator == to perform reference-based comparison e.g. to check both the String reference variable points to the same object. In general, equals() is used to check whether the value of a given String is the same i.e. they contain the same characters in the same sequence or not e.g. "Groovy".equals("Groovy") will be true if you compare them using equals() method. You can also use equalsIgnoreCase() to check if they are equal irrespective of case e.g. "Apple" and "apple" will be the same if you compare them using equalsIgnoreCase() method.
4 ways to read String from File in Java - Example
Just like there are many ways for writing String to text file, there are multiple ways to read String form File in Java. You can use FileReader, BufferedReader, Scanner, and FileInputStream to read text from file. One thing to keep in mind is character encoding. You must use correct character encoding to read text file in Java, failing to do so will result in logically incorrect value, where you don't see any exception but content you have read is completely different than file's original content. Many of the method which is used to read String by default uses platform's default character encoding but they do have overloaded version which accepts character encoding.
Best way to Convert Integer to String in Java with Example
Integer to String conversion in Java
There are many ways to convert an Integer to String in Java e.g. by using Integer.toString(int) or by using String.valueOf(int), or by using new Integer(int).toString(), or by using String.format() method, or by using DecimalFormat, String concatenation, or by using StringBuilder and StringBuffer, etc but which one is the best? Some of them we have already seen on my earlier posts e.g. how to convert int to String and converting double to String. Well, we are going to find the best way to convert Integer to String in Java in this post.
How to convert String to char in Java? Example Tutorial
Hello Java Programmers, if you are wondering how to convert a String to char value in Java then you have come to the right place. Earlier, we have seen how to convert a character to String in Java and today we'll learn opposite i.e. converting String object to a character value. You know the difference right? String is an Object while char is a primitive value. So here we are also going to convert a Java object into a primitive value. By the way, this conversion only make sense if String is a single character. For example, you have a String with value "s", how do you convert that to a char 's' in Java (FYI, string literal are quoted inside double quotes in Java, like "c" and character literals are quoted inside single quotes e.g. 'c' in J)? Well, if you know, Java String is made of a character array and java.lang.String class provides a method toCharArray() to retrieve that character array.
5 Difference between String, StringBuffer, and StringBuilder in Java
Difference between String, StringBuffer, and StringBuilder is probably one of the oldest yet most popular interview question in the history of Java developer interviews. I have personally asked this question almost 4 to 5 times. You will find this question on any list of Java interview questions. I have also included this in my earlier list of core Java questions and Java String questions. If you are preparing for Java interviews, those are handy resources. Now coming back to the answer, although all three classes StringBuffer, StringBuilder, and String are used for representing text data in Java there are some significant differences between them. One of the most notable differences between StringBuilder, StringBuffer, and String in Java is that both StringBuffer and StringBuilder are Mutable classes but String is Immutable in Java. What this means is, you can add, remove or replace characters from StringBuffer and StringBuilder object but any change on the String object like converting uppercase to lowercase or appending a new character using String concatenation will always result in a new String object.
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