replaceAll("match","replace") in java

Question

is there any efficient way to do multiple replaceAll("match","replace").

I'm finding match using regex and replace. e.g.

public static String replacePattern(String line)
{
 if(line != null || !"".equals(line)) 
 {
 line = line.replaceAll("regexPattern_1","replacce_1");
 line = line.replaceAll("regexPattern_2","replacce_2"); 
 line = line.replaceAll("regexPattern_3","replacce_3");
 line = line.replaceAll("regexPattern_4","replacce_4");
 .
 .
 .
 line = line.replaceAll("regexPattern_N","replacce_N");
 return line;
 }
 return line;
}

I don't want code look good, to me Perf is important

• Norsk: There are shorter ways of writing the code sure, but not really any more efficient way of doing, at least not noteworthy so. Think, like a computer, of how many comparisons are needed to do it.
• Florian Schaetz: For ALL cases? Probably not. Depends on your specific requirements.
• leonbloy: Just place the pattern-replace pairs in a HashMap and write a loop
• Norsk: @leonbloy That's not really more efficient, which is what he asked about. But I agree it looks cleaner
• Pshemo: Is scenario like replaceAll("a","b") and then replaceAll("b","c") possible? What result would you want to achieve for input like abc? Should it be bcc or ccc?

Answer 1

Since Strings are immutable another way to handle this:

str.replaceAll("a", "b").replaceAll("c", "d").replaceAll("e", "f");

Answer 2

I'm not sure what you mean by shorter but if you want shorter texts to write you can use:

line = line.replaceAll("regexPattern_1","replacce_1")
 .replaceAll("regexPattern_2","replacce_2") 
 .replaceAll("regexPattern_3","replacce_3")
 .replaceAll("regexPattern_4","replacce_4")
 .
 .
 .
 .replaceAll("regexPattern_N","replacce_N");

Or:

String[] patterns = new String[] {"pattern1",....};
String[] replace = new String[] {"replace1",....};
for(int i=0; i<patterns.length; i++)
{
 line = line.replaceAll(patterns[i],replace[i]);
}

Answer 3

Not sure whether efficiency could be improved. But you can make it look good. If you want more elegance, you can use recursion which will need some additional work for termination.

public static String replacePattern(String line)
{
 //intitialize String[] repl with items to be replaces
 //initialize String[] pattern with corresponding replacements
 for(int i = 0; i<repl.length; i++)
 if(line != null || !"".equals(line)) 
 line = line.replaceAll(repl[i],pattern[i]);
 return line;
}

• Pooya: what do you mean by recursion?
• user6098752: Recursively passing line, arrays replacement strings, array of pattern strings, position parameter. Use position parameter to build a base case
• Pooya: not a good solution for this case which can be solved with one line for loop
• user6098752: Yeah. I just mentioned that it is possible and will look elegant.