How to concatenate substring in StringBuilder?

Question

How can I refactor substring concatenations to StringBuilder?

        String line = "this is my start and my end string";
        int start = line.indexOf("start");
        line = line.substring(0, start) + line.substring(start + 5);

        int end = line.indexOf("end");
        line = line.substring(0, end) + line.substring(end + 3);
            //result: this is my and my string";

How would the same code look like with StringBuilder? When I want to execute substrings several times one after the other?

Have you considered using regular expression?

Rafi Kamal
– Rafi Kamal

2013-10-01 10:02:31 +00:00
Commented Oct 1, 2013 at 10:02 — Rafi Kamal
– Rafi Kamal, Commented Oct 1, 2013 at 10:02

Flavio · Accepted Answer · 2017-02-23 08:07:19Z

4

If your question is "How do I repeatedly remove substrings from a string", you might try something like this:

StringBuilder line = new StringBuilder("this is my start and my end string");
int start = line.indexOf("start");
line.delete(start, start + 5);
int end = line.indexOf("end");
line.delete(end, end + 3);
String result = sb.toString()

Create the StringBuilder once, and then manipulate its contents.

edited Feb 23, 2017 at 8:07

answered Oct 1, 2013 at 10:08

Flavio

12k3 gold badges37 silver badges41 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

anubhava · Accepted Answer · 2013-10-01 10:03:58Z

1

Something like this may be:

    StringBuilder line = new StringBuilder("this is my **start** and my **end** string");
    int start = line.indexOf("start");
    line = new StringBuilder(line.substring(0, start).append(line.substring(start + 5)));

    int end = line.indexOf("end");
    line = new StringBuilder(line.substring(0, end).append(line.substring(end + 3)));

answered Oct 1, 2013 at 10:03

anubhava

790k67 gold badges603 silver badges671 bronze badges

2 Comments

Rafi Kamal Over a year ago

You've declared the variable start two times

anubhava Over a year ago

Thanks, corrected. Sorry it was copy/paste from OP's original post.

Nikhil · Accepted Answer · 2013-10-01 10:04:34Z

1

Something like this you mean? Or have I understood it wrong?

String line = "this is my start and my end string";
int start = line.indexOf("start");
int end = line.indexOf("end");
StringBuilder sb = new StringBuilder();
sb.append(line.substring(0, start);
sb.append(line.substring(start + 5);
sb.append(line.substring(0, end);
sb.append(line.substring(end + 3);
String result = sb.toString()

answered Oct 1, 2013 at 10:04

Nikhil

2,31815 silver badges15 bronze badges

Comments

newuser · Accepted Answer · 2013-10-01 10:06:12Z

0

Try

String line = "this is my start and my end string";
    int start = line.indexOf("start");
    StringBuilder stringBuilder = new StringBuilder();
    stringBuilder.append(line.substring(0, start));
    stringBuilder.append(line.substring(start + 5));

    int end = line.indexOf("end");
    stringBuilder.append(line.substring(0, end));
    stringBuilder.append(line.substring(end + 3));
    System.out.println("StringBuilder : "+stringBuilder.toString());

answered Oct 1, 2013 at 10:06

newuser

8,4862 gold badges28 silver badges33 bronze badges

Comments

Waqas Memon · Accepted Answer · 2013-10-01 10:14:22Z

0

StringBuilder has it's Own indexOf and substring implementations if i am not wrong. The primary concern of the question seems to discard the use of String, and main features of StringBuilder are still concatenations.

So http://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html can help you find relevant methods, and you can go on using StringBuilder with .append() method and ur string finding and substring methods.

answered Oct 1, 2013 at 10:14

Waqas Memon

1,2291 gold badge9 silver badges22 bronze badges

Collectives™ on Stack Overflow

How to concatenate substring in StringBuilder?

5 Answers 5

Comments

2 Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

2 Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related