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String, StringBuffer, and StringBuilder
What are common methods between String and StringBuffer? And what is the difference between string and string buffer?
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6Hm, there is plenty of resources out there, which describes the difference and you can easily see the common methods. So, why do you ask this question here?Danail Nachev– Danail Nachev2011-08-24 08:59:59 +00:00Commented Aug 24, 2011 at 8:59
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4Why don't you look it up yourself in the API?adarshr– adarshr2011-08-24 09:00:23 +00:00Commented Aug 24, 2011 at 9:00
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And to quickly answer your question: String is immutable, while StringBuffer is mutable. When you have complex String, which you cannot construct in single step, you use StringBuffer which is converted to String. When you concatenate strings using '+', Java compiler converts this to calls to StringBuffer under the hood.Danail Nachev– Danail Nachev2011-08-24 09:02:27 +00:00Commented Aug 24, 2011 at 9:02
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u can easily find this in java docs...??? are u interested in where we should use which???amod– amod2011-08-24 09:05:16 +00:00Commented Aug 24, 2011 at 9:05
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yes.May i know where we should use which ? amod0017BoomirajP– BoomirajP2011-08-24 09:16:25 +00:00Commented Aug 24, 2011 at 9:16
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5 Answers
The biggest difference is that String is immutable and StringBuffer is mutable.
Comments
StringBuffer lets you join strings faster. For example the following code:
String s = "Initial string ";
for (int i = 0; i < 100; i++) {
s = s + i;
}
on every iteration creates a string representing integer i and than also creates a new string of s and i joined together and moves s reference to this new object. It does not reuse the same s object by expanding its content.
StringBuffer lets you append string more efficiently. There is also a newer version of this class called StringBuilder which is basically StringBuffer without synchronization.
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The first few lines on the StringBuffer JavaDoc give a pretty good answer:
A thread-safe, mutable sequence of characters. A string buffer is like a
String, but can be modified.
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The most obvious shared methods are those specified by the interface implemented by both String and StringBuffer (as well as StringBuilder): Appendable. It provides 3 methods for appending other values.
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When you need to concatenate many String literal together, then it might be better off for you to use a StringBuffer object, and as when you are done with the concatenation, turning it into a String object using the toString() method.
EDIT: Please ignore the lines below
The below instantiates 6 String objects in the String pool theoretically.
String a = "A" + "B" + "C" + "D" + "E";
5 Comments
Joachim Sauer
In almost all cases a
StringBuilder should be used over a StringBuffer: it provides the exact same API and only lacks synchronization (which is hardly ever useful on a StringBuffer anyway).Joachim Sauer
Sorry to bother you again, but the example you gave does not produce 6 string objects. It produces a single
String, because it's a constant expression.
HJW
@Joachim Sauer I always had the impression that 6 String objects are created, can you please reference me to any materials so that i may correct my understanding? ><
Joachim Sauer