java - Replace only the first specific occurrence -

i want replace spaces in parentheses. code changes spaces in string & don't know why. wrote code this.

public static void main(string[] args) {     scanner scanner = new scanner(system.in);     string line;     line = scanner.nextline();     (int i=0; i<line.length(); i++){         if (line.charat(i)=='('){             while (line.charat(i)!=')'){                 i++;                 if(line.charat(i)==' '){                     line=line.replacefirst(" ", "-space-");                 }             }         }     }     system.out.println(line); } 

just replaced 1 line: spaces in parantheses changed.

public static void main(string[] args) {     scanner scanner = new scanner(system.in);     string line;     line = scanner.nextline();     (int i=0; i<line.length(); i++){         if (line.charat(i)=='('){             while (line.charat(i)!=')'){                 i++;                 if(line.charat(i)==' '){                     // changed                     line = line.substring(0, i) + "-space-" + line.substring(i+1, line.length());                 }             }         }     }     system.out.println(line);          scanner.close(); }