Java String Replace Example Tutorial

This String replace example in Java will show you how to replace String in Java both at character level and by using regular expression.SinceString 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 replacemethods of Stringreturn same String object.String Class in Javaprovides 4 methods to replace String in Java. Thosemethods allow you to replace character from String,replace CharacterSequence fromString, replace all occurrence ofpattern in String or just firstoccurrence of any pattern in Java. We will also see important points on String replace method andhow to make best use ofregular expression while replace string in Java.

This article is on series of my other String article like2 ways to Split String in Java andhow to convert String to Date in Java. String is one of the most important classes in Java and having a good knowledge of String class is mandatory for any Java developer.

Java String Replace Example and Tutorial in Java

String Replace Examples in Java

As I said earlier Java provides at-least four methods toreplace String in Java according to JDK 1.6documentation.

1. Replace method to replacesingle character in String

replace(char oldChar, char newChar)

This replace method in String takes one character and replaces all of its occurrence in provided

String with new character provided to it. Here is anString replace Example of changing character

String replaceSample = "This String replace Example shows how to replace one char from String";

String newString = replaceSample.replace('r', 't');

Output: This Stting teplace Example shows how to teplace one chat ftom Stting

You can see all occurrence of "r" has been replaced by "t".

Important points:

1. This replace method of String will return a new String object if there is a replace.

2. It will return same String objects if there is no matching char and there is no replace.

3. Replacement of String is Case Sensitive, so replacing "c" will only replace small case not CapitalCase.

2. Replace method to replace character sequence in String

replace(CharSequence target, CharSequence replacement)

This String replace method replaces one character sequence with other.This method has added fromJDK 1.5 onwards.Here is aString replace example of replacing character sequence form String

String replaceSample = "String replace Example of replacing Character Sequence";

String newString = replaceSample.replace("re", "RE");

Output: String REplace Example of REplacing Character Sequence

In this String replace Example, we have replaced "re" with "RE".

Important points:

1) This String replace method willthrowNullPointerException if either oldCharSequence or newCharSequenceis null.

2) Replacement of Stringstarts from beginning and proceed towards end. So ina String "ccc" replacing"cc" with "d" will result in "dc" rather than "cd".

3. Replace method to replace all matched pattern in String

replaceAll(String regex, String replacement)

Good thing about replace method of StringClass in Javais that it supports regular expression.With regex capability you can perform sophisticatedSearch on String and than replace characters.This String replace methodreplaces each matched substring with the replacement String provided. Let's see String replace examplewith regular expression:

String replaceSample = "String replace Example with regular expression";

String newString = replaceSample.replaceAll("^S","R");

Output: Rtring replace Example with regular expression

This String replace replaces any "S" wiht "R" if it comes at beginning of line "^" denotes beginning of line you can alsoapply pattern matching wildcards and charset while replacing String in Java.

Important points:

1. This String replace method will throwPatternSyntaxException in caseregular expression's syntax is not valid.

4. Replace method to replace first matched pattern in String

replaceFirst(String regex, String replacement)

This String replace method is similar to above method but it only replaces first occurrence of matchingpattern instead of all occurrence. Very handy some time.Here is an example of String replace withreplaceFirst() method.

String replaceSample = "String replace Example with replaceFirst";

String newString = replaceSample.replaceFirst("re","RE");

Output: String REplace Example with replaceFirst

You can see only first occurrence of "re" is replaced with "RE" while second occurrence remains same

That’s all on how to replace String in Java, search and replace is one of the most needed thing in String and having an idea of right way of doing it is good. These String replace examples are rather simple but you can make more sophisticated by using regular expression.

Other Java Tutorials

How to Convert Date to String in Java

How to Convert Sting to double in Java

How to override CompareTo in Java

How to override Equals in java

How to implement Thread in Java

Spring Interview questions in java

JSP Interview questions in java

Read more: http://javarevisited.blogspot.com/2011/12/java-string-replace-example-tutorial.html#ixzz2ki3ClW3k