How is concatenation of final strings done in Java?

by

http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.28 says that

Simple names (§6.5.6.1) that refer to constant variables (§4.12.4) are constant expressions.

http://docs.oracle.com/javase/specs/jls/se8/html/jls-15.html#jls-15.28 also says:

A constant expression is an expression denoting a value of primitive type or a String that does not complete abruptly and is composed using only the following:

  • Literals of primitive type and literals of type String (§3.10.1, §3.10.2, §3.10.3, §3.10.4, §3.10.5)
  • […]
  • The additive operators + and – (§15.18)
  • […]
  • Simple names (§6.5.6.1) that refer to constant variables (§4.12.4).

Example 15.28-1. Constant Expressions

[…]

“The integer ” + Long.MAX_VALUE + ” is mighty big.”

Since those two variables are constant expressions, the compiler does the concatenation:

String str = str1 + str2;

is compiled the same way as

String str = "str" + "ing";

which is compiled the same way as

String str = "string";

More Related Contents:

  1. Comparing strings with == which are declared final in Java
  2. Why is the String class declared final in Java?
  3. Need some advice on split() method in Java [closed]
  4. StringBuilder vs String concatenation in toString() in Java
  5. Sort on a string that may contain a number
  6. Check string for palindrome
  7. length and length() in Java
  8. How to format a Java string with leading zero?
  9. Is String Literal Pool a collection of references to the String Object, Or a collection of Objects
  10. Convert array of strings into a string in Java
  11. How to insert a character in a string at a certain position?
  12. Getting value of public static final field/property of a class in Java via reflection
  13. How to shuffle characters in a string without using Collections.shuffle(…)?
  14. Closing a Scanner throws java.util.NoSuchElementException
  15. Which loop has better performance? Why?
  16. Changing private final fields via reflection
  17. Is conversion to String using (“” + ) bad practice?
  18. Convert binary string to byte array
  19. What is the best way to extract the first word from a string in Java?
  20. How to replace ” \ ” with ” \\ ” in java
  21. Java split is eating my characters
  22. Efficient way to compare version strings in Java [duplicate]
  23. Case insensitive matching in Java switch-case statement
  24. How many Java string objects created in the code String s=”abc”+”xyz”;?
  25. What’s the best way to check if a String contains a URL in Java/Android?
  26. What’s the quickest way to compare strings in Java?
  27. Random element from string array [closed]
  28. Hints for java.lang.String.replace problem? [duplicate]
  29. How to convert a Java String to an ASCII byte array?
  30. What is difference between mutable and immutable String in java

Leave a Comment