String builder vs string concatenation [duplicate]

by

In your particular example, none because the compiler internally uses StringBuilders to do String concatenation. If the concatenation occurred in a loop, however, the compiler could create several StringBuilder and String objects. For example:

String s= "" ;
for(int i= 0 ; i < 10 ; i++ )
    s+= "a" ;

Each time line 3 above is executed, a new StringBuilder object is created, the contents of s appended, “a” appended, and then the StringBuilder is converted into a String to be assigned back to s. A total of 10 StringBuilders and 10 Strings.

Conversely, in

StringBuilder sb= new StringBuilder() ;
for(int i= 0 ; i < 10 ; i++ )
    sb.append( "a" );
String s= sb.toString() ;

Only 1 StringBuilder and 1 String are created.

The main reason for this is that the compiler could not be smart enough to understand that the first loop is equivalent to the second and generate more efficient (byte) code. In more complex cases, it’s impossible even for the smartest compiler to know. If you absolutely need this optimization, you have to introduce it manually by using StringBuilders explicitly.

More Related Contents:

  1. how to get elements from JSONObject and write it to file
  2. StringBuilder vs String concatenation in toString() in Java
  3. Difference between StringBuilder and StringBuffer
  4. How do I concatenate two strings in Java?
  5. String, StringBuffer, and StringBuilder
  6. Concatenating null strings in Java [duplicate]
  7. Why StringBuilder when there is String?
  8. How to concatenate int values in java?
  9. How is String concatenation implemented in Java 9?
  10. Why to use StringBuffer in Java instead of the string concatenation operator
  11. How can I clear or empty a StringBuilder? [duplicate]
  12. Java: String concat vs StringBuilder – optimised, so what should I do?
  13. Remove last character of a StringBuilder?
  14. Does concatenating strings in Java always lead to new strings being created in memory?
  15. Java String literals concatenation
  16. Correct way to use StringBuilder in SQL
  17. How to convert byte array to hex format in Java
  18. How do I prove programmatically that StringBuilder is not threadsafe?
  19. What is the difference between String and StringBuffer in Java?
  20. Most efficient solution for reading CLOB to String, and String to CLOB in Java?
  21. StringBuilder capacity()
  22. String equals and == with String concatenation [duplicate]
  23. Why StringJoiner when we already have StringBuilder?
  24. Nesting method calls in java
  25. Create a file from a photo URI on Android
  26. AutoComplete ComboBox in JavaFX
  27. SSLHandshakeException: No subject alternative names present
  28. How to make HashMap work with Arrays as key?
  29. File exists and IS directory, but listFiles() returns null
  30. Immutable Type: public final fields vs. getter

Leave a Comment