Can we use the + sign to add a string literal in a StringBuffer?

Question

StringBuffer sb = new StringBuffer();

sb.append("New "+"Delhi");

and other is:

sb.append("New ").append("Delhi");

both will print "New Delhi".

Which one is better and why?

Because some times to save time I use "+" instead of ".append".

The compiler probably turns that into a single string literal, so no work is done to concatenate the strings. — Andy Turner, Oct 06 '15 at 06:09
Possible duplicate of [StringBuilder/StringBuffer vs. "+" Operator](http://stackoverflow.com/questions/4648607/stringbuilder-stringbuffer-vs-operator) — Madhukar Hebbar, Oct 06 '15 at 06:12

score 4 · Answer 1 · answered Oct 06 '15 at 06:23

sb.append("New "+"Delhi"):

public class Test {
  public Test();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class java/lang/StringBuffer
       3: dup
       4: invokespecial #3                  // Method java/lang/StringBuffer."<init>":()V
       7: astore_1
       8: aload_1
       9: ldc           #4                  // String New Delhi
      11: invokevirtual #5                  // Method java/lang/StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
      14: pop
      15: return
}

sb.append("New ").append("Delhi"):

Compiled from "Test.java"
public class Test {
  public Test();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public static void main(java.lang.String[]);
    Code:
       0: new           #2                  // class java/lang/StringBuffer
       3: dup
       4: invokespecial #3                  // Method java/lang/StringBuffer."<init>":()V
       7: astore_1
       8: aload_1
       9: ldc           #4                  // String New
      11: invokevirtual #5                  // Method java/lang/StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
      14: ldc           #6                  // String Delhi
      16: invokevirtual #5                  // Method java/lang/StringBuffer.append:(Ljava/lang/String;)Ljava/lang/StringBuffer;
      19: pop
      20: return
}

As the above bytecode, for static string:

when using "+", the javac compiler will auto concat it a String.
when using "append", the javac compiler will auto expand as two String variables.

so for static string, the "+" is good for using.

Abhijeet Kale · Answer 2 · 2015-10-06T06:30:25.640

0

any string append operation is converted into StringBuilder internally like

"The answer is: " + value

is converted into :

new StringBuilder("The answer is: ")).append(value).toString()

If any expression getting concatenated is not constant , .append is a better approach.

so in your case doesn't matter performance wise which way you write. Only '+' will improve readability of your code.

edited Oct 06 '15 at 06:30

answered Oct 06 '15 at 06:13

Abhijeet Kale

1,656
1
16
34

Edits are answering the question. – Abhijeet Kale Oct 06 '15 at 06:18

score 0 · Answer 3 · edited Oct 06 '15 at 06:40

0

Constant string concatenations will be replaced at compile-time.

You should use a Stringbuilder/Stringbuffer if you concatenate variable strings e.g. variables, especially when you do the concatenations in a loop.

edited Oct 06 '15 at 06:40

chrisb2244

2,940
22
44

answered Oct 06 '15 at 06:13

Fabian Lang

78
1
8

score 0 · Answer 4 · answered Oct 06 '15 at 06:16

"+" sign is used to add a string at the end of another string. Now, as per your question, whenever append() is used with String Buffer to append character sequence or string at that time append function internally performing to concatenate string using "+" sign.

Can we use the + sign to add a string literal in a StringBuffer?

4 Answers4