CODEWITHSUNDEEP
javastringreplacestringbuilderoverwrite
Kevin Rave
Kevin Rave

Reputation: 14426

StringBuilder - replace existing string entirely. Any method?

I see String usage in the existing code with several concatenation. Sonar code coverage recommends using StringBuilder. I am updating the code to use StringBuilder. But I am wondering how to efficiently overwrite the existing content with a new string.

In the string representation, its like below:

String query = "select...";
if ( x ) {
    query = "select xyz...";
}

With StringBuilder, I used this:

 StringBuilder query = new StringBuilder("select...");
 if ( x ) {
     // I need to overwrite the existing stringbuilder content here
     query = new StringBuilder("Select xyz..");
        //or
     query = query.replace(,,,);
        //or
     //Anything better
 }

I was hoping there would be a method like:

 query.replace("new string");

which overwrites entire existing string with the new string. But it is not available.

Upvotes: 3

Views: 12088

Answers (3)

Simon Baars
Simon Baars

Reputation: 2289

For your usecase the following seems perfect:

private static final String SELECT_PRE = "Select";
private static final String SELECT_POST = "...";
StringBuilder query = new StringBuilder(SELECT_PREFIX+SELECT_POST);
if ( x ) {
     query = query.insert(SELECT_PREFIX.length(), " xyz");
}

Upvotes: 0

Steven
Steven

Reputation: 525

Here is one solution, not the most elegant one, using StringBuilder.replace(int start, int end, String str)
Let's say there are two conditions:

  • Condition1: you want to replace "ele" with "xxx"
  • Condition2: you want to replace "..." with "yyy"

Try the following

StringBuilder query = new StringBuilder("select...");
String x = "ele";

String term1 = "ele";
String newTerm1 = "xxx";
String term2 = "...";
String newTerm2 = "yyy";

if ( x.equals(term1) ) {
    int start = query.indexOf(term1);
    int end = start + term1.length();
    query.replace(start, end, newTerm1);

}
else if (x.equals(term2)){
    int start = query.indexOf(term2);
    int end = start + term2.length();
    query.replace(start, end, newTerm2);
}
System.out.println(query.toString());

Upvotes: 0

arynaq
arynaq

Reputation: 6870

query.replace(0,query.length(), "new string");

Should work.

Upvotes: 11

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