Replace a character at a specific index in a string

Question

I m trying to replace a character at a specific index in a string    What I m doing is   String myName    domanokz   myName charAt 4     x     This gives an error   Is there any method to do this

User · Answer

String is an immutable class in java  Any method which seems to modify it always returns a new string object with modification   If you want to manipulate a string  consider StringBuilder or StringBuffer in case you require thread safety

User · Answer

As previously answered here  String instances are immutable  StringBuffer and StringBuilder are mutable and suitable for such a purpose whether you need to be thread safe or not   There is however a way to modify a String but I would never recommend it because it is unsafe  unreliable and it can can be considered as cheating   you can use reflection to modify the inner char array the String object contains  Reflection allows you to access fields and methods that are normally hidden in the current scope  private methods or fields from another class       public static void main String   args        String text    This is a test       try             String value is the array of char  char              that contains the text of the String         Field valueField   String class getDeclaredField  value              String value is a private variable so it must be set as accessible            to read and or to modify its value         valueField setAccessible true             now we get the array the String instance is actually using         char   value    char   valueField get text             The 13rd character is the  s  of the word  Test          value 12   x             We display the string which should be  This is a text          System out println text         catch  NoSuchFieldException   SecurityException e            e printStackTrace          catch  IllegalArgumentException e            e printStackTrace          catch  IllegalAccessException e            e printStackTrace

User · Answer

this will work     String myName  domanokz      String p myName replace myName charAt 4   x       System out println p     Output   domaxokz

User · Answer

Turn the String into a char    replace the letter by index  then convert the array back into a String   String myName    domanokz   char   myNameChars   myName toCharArray    myNameChars 4     x   myName   String valueOf myNameChars

User · Answer

First thing I should have noticed is that charAt is a method and assigning value to it using equal sign won t do anything  If a string is immutable  charAt method  to make change to the string object must receive an argument containing the new character  Unfortunately  string is immutable  To modify the string  I needed to use StringBuilder as suggested by Mr  Petar Ivanov

User · Answer

You can overwrite a string  as follows     String myName    halftime   myName   myName substring 0 4   x  myName substring 5       Note that the string myName occurs on both lines  and on both sides of the second line     Therefore  even though strings may technically be immutable  in practice  you can treat them as editable by overwriting them

User · Answer

String are immutable in Java  You can t change them   You need to create a new string with the character replaced   String myName    domanokz   String newName   myName substring 0 4   x  myName substring 5     Or you can use a StringBuilder   StringBuilder myName   new StringBuilder  domanokz    myName setCharAt 4   x     System out println myName

User · Answer

I agree with Petar Ivanov but it is best if we implement in following way   public String replace String str  int index  char replace            if str  null           return str       else if index lt 0    index gt  str length             return str            char   chars   str toCharArray        chars index    replace      return String valueOf chars

[java] Replace a character at a specific index in a string?

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