Java String replaceAll()

The Java String class replaceAll() method returns a string replacing all the sequence of characters matching regex and replacement string.

Signature

Parameters

regex : regular expression

replacement : replacement sequence of characters

Returns

replaced string

Exception Throws

PatternSyntaxException: if the syntax of the regular expression is not valid.

Internal implementation

  public String replaceAll(String regex, String replacement) {          return Pattern.compile(regex).matcher(this).replaceAll(replacement);  }  

Java String replaceAll() example: replace character

Let’s see an example to replace all the occurrences of a single character.

FileName: ReplaceAllExample1.java

  public class ReplaceAllExample1{  public static void main(String args[]){  String s1=”tutoraspire is a very good website”;  String replaceString=s1.replaceAll(“a”,”e”);//replaces all occurrences of “a” to “e”  System.out.println(replaceString);  }}  

Test it Now

Output:

jevetpoint is e very good website

Java String replaceAll() example: replace word

Let’s see an example to replace all the occurrences of a single word or set of words.

FileName: ReplaceAllExample2.java

  public class ReplaceAllExample2{  public static void main(String args[]){  String s1=”My name is Khan. My name is Bob. My name is Amit singh.”;  String replaceString=s1.replaceAll(“is”,”was”);//replaces all occurrences of “is” to “was”  System.out.println(replaceString);  }}  

Test it Now

Output:

My name was Khan. My name was Bob. My name was Tutoraspire.

Java String replaceAll() example: remove white spaces

Let’s see an example to remove all the occurrences of white spaces.

FileName: ReplaceAllExample3.java

  public class ReplaceAllExample3{  public static void main(String args[]){  String s1=”My name is Khan. My name is Bob. My name is Amit singh.”;  String replaceString=s1.replaceAll(“\s”,””);  System.out.println(replaceString);  }}  

Test it Now

Output:

MynameisKhan.MynameisBob.Mynameisamitsingh.

Java String replaceAll() Method Example 4

The replaceAll() method throws the PatternSyntaxException when there is an improper regular expression. Look at the following example.

FileName: ReplaceAllExample4.java

  public class ReplaceAllExample4   {  // main method  public static void main(String argvs[])  {    // input string  String str = “For learning Java, TutorAspire is a very good site.”;    System.out.println(str);    String regex = “\”; // the regular expression is not valid.    // invoking the replaceAll() method raises the PatternSyntaxException  str = str.replaceAll(regex, “TutorAspire “);    System.out.println(str);    }  }  

Output:

For learning Java, TutorAspire is a very good site.    Exception in thread "main" java.util.regex.PatternSyntaxException: Unexpected internal error near index 1    at java.base/java.util.regex.Pattern.error(Pattern.java:2015)  at java.base/java.util.regex.Pattern.compile(Pattern.java:1784)  at java.base/java.util.regex.Pattern.(Pattern.java:1427)  at java.base/java.util.regex.Pattern.compile(Pattern.java:1068)  at java.base/java.lang.String.replaceAll(String.java:2126)  at ReplaceExample4.main(ReplaceExample4.java:12)

Java String replaceAll() Method Example 5

The replaceAll() method can also be used to insert spaces between characters.

FileName: ReplaceAllExample5.java

  public class ReplaceAllExample5   {  // main method  public static void main(String argvs[])  {    // input string  String str = “TutorAspire”;  System.out.println(str);    String regex = “”;  // adding a white space before and after every character of the input string.  str = str.replaceAll(regex, ” “);    System.out.println(str);    }  }  

Output:

TutorAspire   J a v a T p o i n t

Java String replaceAll() Method Example 6

Even the null regular expression is also not accepted by the replaceAll() method as the NullPointerException is raised.

FileName: ReplaceAllExample6.java

  public class ReplaceAllExample6   {  // main method  public static void main(String argvs[])  {    // input string  String str = “TutorAspire”;  System.out.println(str);    String regex = null; // regular expression is null    str = str.replaceAll(regex, ” “);    System.out.println(str);    }  }  

Output:

TutorAspire    Exception in thread "main" java.lang.NullPointerException  at java.base/java.util.regex.Pattern.(Pattern.java:1426)  at java.base/java.util.regex.Pattern.compile(Pattern.java:1068)  at java.base/java.lang.String.replaceAll(String.java:2126)  at ReplaceAllExample6.main(ReplaceAllExample6.java:13)

Next TopicJava String split()

Java String replaceAll() method

Java String replaceAll()

Signature

Parameters

Returns

Exception Throws

Internal implementation

Java String replaceAll() example: replace character

Java String replaceAll() example: replace word

Java String replaceAll() example: remove white spaces

Java String replaceAll() Method Example 4

Java String replaceAll() Method Example 5

Java String replaceAll() Method Example 6

Scatter | Gather | Vectored IO

C# Implicitly Typed Local Variable

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