Replace all occurrences of a String using StringBuilder

Question

Am I missing something  or does StringBuilder lack the same  replace all occurrences of a string A with string B  function that the normal String class does  The StringBuilder replace function isn t quite the same  Is there any way to this more efficiently without generating multiple Strings using the normal String class

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java util regex Pattern matcher CharSequence s  can use a StringBuilder as an argument so you can find and replace each occurence of your pattern using start   and end   without calling builder toString

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Use the following         Utility method to replace the string from StringBuilder     param sb          the StringBuilder object     param toReplace   the String that should be replaced     param replacement the String that has to be replaced by        public static void replaceString StringBuilder sb                                   String toReplace                                   String replacement              int index   -1      while   index   sb lastIndexOf toReplace      -1            sb replace index  index   toReplace length    replacement

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How about create a method and let String replaceAll do it for you   public static void replaceAll StringBuilder sb  String regex  String replacement        String aux   sb toString        aux   aux replaceAll regex  replacement       sb setLength 0       sb append aux

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Well  you can write a loop   public static void replaceAll StringBuilder builder  String from  String to        int index   builder indexOf from       while  index    -1                builder replace index  index   from length    to           index    to length       Move to the end of the replacement         index   builder indexOf from  index             Note that in some cases it may be faster to use lastIndexOf  working from the back  I suspect that s the case if you re replacing a long string with a short one - so when you get to the start  any replacements have less to copy  Anyway  this should give you a starting point

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You could use Pattern Matcher   From the Matcher javadocs    Pattern p   Pattern compile  cat     Matcher m   p matcher  one cat two cats in the yard     StringBuffer sb   new StringBuffer     while  m find           m appendReplacement sb   dog        m appendTail sb    System out println sb toString

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Even simple one is using the String ReplaceAll function itself  You can write it as  StringBuilder sb   new StringBuilder  Hi there  are you there    System out println Pattern compile  there   matcher sb  replaceAll  niru

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Adam  I think in your code snippet you should track the start position for m find   because string replacement may change the offset after the last character matched   public static void replaceAll StringBuilder sb  Pattern pattern  String replacement        Matcher m   pattern matcher sb       int start   0      while  m find start             sb replace m start    m end    replacement           start   m start     replacement length

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I found this method  Matcher replaceAll String replacement   In java util regex Matcher java you can see more           Replaces every subsequence of the input sequence that matches the    pattern with the given replacement string         lt p gt  This method first resets this matcher   It then scans the input    sequence looking for matches of the pattern   Characters that are not    part of any match are appended directly to the result string  each match    is replaced in the result by the replacement string   The replacement    string may contain references to captured subsequences as in the   link     appendReplacement appendReplacement  method         lt p gt  Note that backslashes   lt tt gt   lt  tt gt   and dollar signs   lt tt gt   lt  tt gt   in    the replacement string may cause the results to be different than if it    were being treated as a literal replacement string  Dollar signs may be    treated as references to captured subsequences as described above  and    backslashes are used to escape literal characters in the replacement    string         lt p gt  Given the regular expression  lt tt gt a b lt  tt gt   the input     lt tt gt  aabfooaabfooabfoob  lt  tt gt   and the replacement string     lt tt gt  -  lt  tt gt   an invocation of this method on a matcher for that    expression would yield the string  lt tt gt  -foo-foo-foo-  lt  tt gt          lt p gt  Invoking this method changes this matcher s state   If the matcher    is to be used in further matching operations then it should first be    reset    lt  p gt         param  replacement            The replacement string        return  The string constructed by replacing each matching subsequence             by the replacement string  substituting captured subsequences             as needed     public String replaceAll String replacement        reset        StringBuffer buffer   new StringBuffer input length         while  find              appendReplacement buffer  replacement             return appendTail buffer  toString

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Look at JavaDoc of replaceAll method of String class      Replaces each substring of this string that matches the given regular   expression with the given replacement   An invocation of this method   of the form str replaceAll regex  repl  yields exactly the same result   as the expression       java util regex Pattern compile regex  matcher str  replaceAll repl    As you can see you can use Pattern and Matcher to do that

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The class org apache commons lang3 text StrBuilder in Apache Commons Lang allows replacements   public StrBuilder replaceAll String searchStr  String replaceStr      This does not receive a regular expression but a simple string

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public static String replaceCharsNew String replaceStr Map lt String String gt  replaceStrMap           StringBuilder replaceStrBuilder   new StringBuilder replaceStr           Set lt String gt  keys replaceStrMap keySet            for String invalidChar keys               int index   -1              while  index replaceStrBuilder indexOf invalidChar index     -1                   replaceStrBuilder replace index index invalidChar length   replaceStrMap get invalidChar                                    return replaceStrBuilder toString

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Here is an in place replaceAll that will modify the passed in StringBuilder  I thought that I would post this as I was looking to do replaceAll with out creating a new String   public static void replaceAll StringBuilder sb  Pattern pattern  String replacement        Matcher m   pattern matcher sb       while m find              sb replace m start    m end    replacement             I was shocked how simple the code to do this was  for some reason I thought changing the StringBuilder while using the matcher would throw of the group start end but it does not    This is probably faster than the other regex answers because the pattern is already compiled and your not creating a new String but I didn t do any benchmarking

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Yes  It is very simple to use String replaceAll   method   package com test   public class Replace        public static void main String   args            String input    Hello World           input   input replaceAll  o    0            System out println input             Output   Hell0 W0rld   If you really want to use StringBuilder replace int start  int end  String str  instead then here you go   public static void main String args          StringBuilder sb   new StringBuilder  This is a new StringBuilder         System out println  Before      sb        String from    new       String to    replaced       sb   sb replace sb indexOf from   sb indexOf from    from length    to        System out println  After      sb       Output   Before  This is a new StringBuilder After  This is a replaced StringBuilder

[java] Replace all occurrences of a String using StringBuilder?

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