I have a string
String s="my name is ${name}. My roll no is ${rollno} "
I want to do string operations to update the name and rollno using a method.
public void name(String name, String roll)
{
String new = s.replace(" ${name}", name).replace(" ${rollno}", roll);
}
Can we achieve the same using some other means like using regex to change after first "$" and similarly for the other?
You can use either Matcher#appendReplacement or Matcher#replaceAll (with Java 9+):
A more generic version:
String s="my name is ${name}. My roll no is ${rollno} ";
Matcher m = Pattern.compile("\\$\\{([^{}]+)\\}").matcher(s);
Map<String,String> replacements = new HashMap();
replacements.put("name","John");
replacements.put("rollno","123");
StringBuffer replacedLine = new StringBuffer();
while (m.find()) {
if (replacements.get(m.group(1)) != null)
m.appendReplacement(replacedLine, replacements.get(m.group(1)));
else
m.appendReplacement(replacedLine, m.group());
}
m.appendTail(replacedLine);
System.out.println(replacedLine.toString());
// => my name is John. My roll no is 123
Java 9+ solution:
Matcher m2 = Pattern.compile("\\$\\{([^{}]+)\\}").matcher(s);
String result = m2.replaceAll(x ->
replacements.get(x.group(1)) != null ? replacements.get(x.group(1)) : x.group());
System.out.println( result );
// => my name is John. My roll no is 123
See the Java demo.
The regex is \$\{([^{}]+)\}:
\$\{ - a ${ char sequence([^{}]+) - Group 1 (m.group(1)): any one or more chars other than { and }\} - a } char.See the regex demo.
m.group(1) is a method of m Matcher object that gets the string value of the first capturing group in the regular expression.