Why doesn't the first line replace "(" with an empty string , while the second one does?
public static void main(String []args){
String a="This(rab)(bar)";
a=a.replace("\\(",""); //First
String b=a.replaceFirst("\\(","");//Second
System.out.println(a + " "+b);
}
There is a difference between replace and replaceFirst. If your IDE shows you the method signatures, you'll see:
See how replace accepts a plain old target whereas replaceFirst accepts a regex?
"\\(" is a regex that means "a single open parenthesis". replace doesn't treat the strings you pass in as regexes. It will simply try to find a backslash followed by an open parenthesis, which does not exist in your string.
If you want to use replace, just use "(".
( is not a valid regex. It doesn’t mean “match an open parenthesis”. \( is valid regex that means “Match an open parenthesis”. In java string literals, the backslash gets escapes to become `\`.\( is a regex that means “one opening parenthesis” and replaceFirst accepts a regex. ( on its own has special meaning in regex - start of a capturing group, so you need to escape it with `` to mean “one open parenthesis”. @ErikNouroyanFor replace to work you should write:
a=a.replace("(",""); //First
or use replaceAll if you want to pass a regex:
a=a.replaceAll("\\(",""); //First
replace accepts a sequence of characters to replace:
public String replace(CharSequence target, CharSequence replacement)
Therefore, in your case it attempts to replace the 3 characters "\(", not just the single character "(".
replace does not expect a regex as the first argument. Therefore it tried to replace the actual sub-string "\\(", which is not present in a.The problem is that it is running in replace with several characters and, therefore, what it will look for is \ and (, so that this does not happen the quotation marks should only contain the character to replace :
a = a.replace("(", ""); // First
Next I leave a sniper with the original proposal and the fixed one :
public class Main {
private static final Main initRun = new Main();
public static void main(String[] args) {
String a = "This(rab)(bar)";
System.out.println("Original");
initRun.runOriginal(a);
System.out.println("Fixed");
initRun.runFixed(a);
// Output
// Original
// This(rab)(bar)
// Thisrab)(bar)
// Fixed
// Thisrab)bar)
// Thisrab)bar)
}
/**
* Execute the original proposal
*
* @param a String for replace
*/
void runOriginal(String a) {
a = a.replace("\\(", ""); // First
String b = a.replaceFirst("\\(", "");// Second
System.out.println(a + "\n" + b);
}
/**
* Execute the fixed proposal
*
* @param a String for replace
*/
void runFixed(String a) {
a = a.replace("(", ""); // First
String b = a.replaceFirst("\\(", "");// Second
System.out.println(a + "\n" + b);
}
}
