Java String replace Code

This String replace example in Java will show you how to replace String in Java both at character level and by using regular expression. Since String is final in Java every time you replace String you will get a new String object only if your actually replace anything on original String otherwise replace methods of String return same String object.

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How to replace String: character substring replaceAll example
In this Java tutorial, we will see How to replace characters and substring from String in Java. First example in this program replaces a character, i.e. it replaces "J" with "K", which creates "Kava" from "Java". Second String replace example, replaces words from String, it replaces Scala with Java. Third and fourth example shows how to use regular expression to replace String in Java. Both examples uses \\s to match spaces or any white space character and replace with #. Third one uses replaceFirst() which only replace first match, while fourth one uses replaceAll() which replaces all matches.

Hidden evils of Java’s String.split() and replace()
If you code in Java, you have inevitably used the String.split() and String.replace() (including replaceFirst() and replaceAll()) functions. And why wouldn’t you? They are much more convenient than using the Java Regular Expressions API where you need to create a ‘Pattern‘ object, and possibly a ‘Matcher‘, and then call methods on those.

How to remove XML special characters from Java String with Example
There are two approaches to replace XML or HTML special characters from Java String, First, Write your own function to replace XML special characters or use any open source library which has already implemented it. Luckily there is one very common open source library which provides function to replace special characters from XML String is Apache commons lang’s StringEscapeUtils class which provide escaping for several languages like XML, SQL and HTML. you can use StringEscapeUtils to convert XML special character in String to there escaped equivalent. I personally like to use open source code instead of reinventing the wheel to avoid any testing efforts.

Top 10 Questions for Java Regular Expression
How to extract numbers from a string? How to split Java String by newlines? Importance of Pattern.compile()? How to escape text for regular expression? Why does String.split() need pipe delimiter to be escaped? How to replace 2 or more spaces with single space in string and delete leading spaces only? and many more...

String vs StringBuffer vs StringBuilder
Difference between String, Stringbuffer and StringBuilder: In this Java tutorial we will see What is String in Java, some important properties of String in Java, What is StringBuffer in Java , When to use StringBuffer in Java , StringBuilder in Java and how it can be used in place of StringBuffer, What are differences between String and StringBuffer and StringBuilder in Java which is a frequently asked core Java question and mostly String vs StringBuilder vs StringBuffer.

Java String is Special
A Java String contains an immutable sequence of Unicode characters. Unlike C/C++, where string is simply an array of char, A Java String is an object of the class java.lang. Java String is, however, special. Unlike an ordinary class:

5 ways to check if String is empty
String in Java is considered empty if its not null and it’s length is zero. By the way before checking length you should verify that String is not null because calling length() method on null String will result in java.lang.NullPointerException. Empty String is represented by String literal “”. Definition of empty String may be extended to those String as well which only contains white space but its an specific requirement and in general String with white space are not considered as empty String in Java. Since String is one of the most frequently used class and commonly used in method arguments, we often needs to check if String is empty or not. Thankfully there are multiple ways to find if String is empty in Java or not. You can also count number of characters in String, as String is represented as character array and decide if String is empty or not. If count of characters is zero than its an empty String. In this Java String tutorial we going to see 5 ways to find if any String in Java is empty or not. Here are our five ways to check empty String :

Summary of the String Class
A Java String contains an immutable sequence of Unicode characters. Unlike C/C++, where string is simply an array of char, A Java String is an object of the class java.lang.

Why String is immutable or final
This is one of the most popular String Interview questions in Java, which starts with discussion of, What is String, How String in Java is different than String in C and C++, and then shifted towards what is immutable object in Java , what are the benefits of immutable object , why do you use it and which scenarios do you use it. This is some time also asked as "Why String is final in Java".

How to convert String to Date
SimpleDateFormat in Java can be used to convert String to Date in Java. java.text.SimpleDateFormat is an implementation of DateFormat which defines a date pattern and can convert a particular String which follows that pattern into Date in Java.This is the second part of the article on java.util.Date and String in Java. In the first part we have seen How to convert Date to String in Java. SimpleDateFormat accepts a String in any date format e.g. yyyyMMdd is a date pattern and 20110924 is a String in that format. Now you want to create a java.util.Date object from this String.

What is String Interning?
String Interning is a method of storing only one copy of each distinct String Value, which must be immutable. In Java, String class has a public method intern() that returns a canonical representation for the string object. Java’s String class privately maintains a pool of strings, where String literals are automatically interned.

Java String replaceAll() method example
This java tutorial shows how to use the replaceAll() method of java.lang.String class. This method returns a new String object as a result of replacing all the occurrences of the regex pattern with String parameter replacement.

How to convert Java Collection to comma separated String
Many times we need to convert any Collection like Set or List into String like comma separated or any other delimiter delimited String. Though this is quite a trivial job for a Java programmer as you just need to Iterate through loop and create a big String where individual String are separated by delimiter, you still need to handle cases like last element should not have delimiter or at bare minimum you need to test that code.

Java String class or object
Strigns are sequence of characters in any language. For java, sequence of characters are stored in the form of java.lang.String object.
Strings are immutable objects, meaning once created, the contents of the string, can not be modified in memory that means string objects are readonly.

Strings in Java
This article explains how String are handled in Java. It provides deep insight on how String objects can be manipulated using variuos methods provided by String class.

Convert String to Date
In this example we are going to convert String into date. In java date conversion, two packages are used .They are java.util.* and java.text.*. The java.util.* package provides three subclasses that are named as java.util.Date, java.util.Time and java.util.Timestamp class.

String replaceFirst() Method
The java.lang.String.replace(CharSequence target, CharSequence replacement) method replaces each substring of this string that matches the literal target sequence with the specified literal replacement sequence. The replacement proceeds from the beginning of the string to the end:

Java's character and assorted string classes support text-processing
Text can represent a combination of digits, letters, punctuation, words, sentences, and more. Computer programs that process text need assistance (from their associated languages) to represent and manipulate text. Java provides such assistance through the Character, String, StringBuffer, and StringTokenizer classes. In this article, you'll create objects from these classes and examine their various methods. You'll also receive answers to three mysteries: why Java regards a string literal as a String object, why String objects are immutable (and how immutability relates to string internment), and what happens behind the scenes when the string concatenation operator concatenates two strings into a single string.

Strings in Java
The String class is commonly used for holding and manipulating strings of text in Java programs. It is found in the standard java.lang package which is automatically imported, so you don't need to do anything special to use it.
In its simplest form, you use the String class by typing some text surrounded by double quotes. This is called a String literal.

Java Native Interface Introduction
JNI stands for Java Native Interface JNI specifies a communication protocol between Java code and external, native code. It enables your Java code to interface with native code written in other languages (such as C, C++) Native code typically accesses the CPU and registers directly and is thus faster than interpreted code (like Java) Java native methods are methods declared in your Java code (much like you declare an abstract method), but which are actually implemented in another programming language.