Java ‘+’ operator between Arithmetic Add & String concatenation? [duplicate]

by

This is basic operator precedence, combined with String concatenation vs numerical addition.

Quoting:

If only one operand expression is of type String, then string
conversion (§5.1.11) is performed on the other operand to produce a
string at run time.

The result of string concatenation is a reference to a String object
that is the concatenation of the two operand strings. The characters
of the left-hand operand precede the characters of the right-hand
operand in the newly created string.

The String object is newly created (§12.5) unless the expression is a
constant expression (§15.28).

An implementation may choose to perform conversion and concatenation
in one step to avoid creating and then discarding an intermediate
String object. To increase the performance of repeated string
concatenation, a Java compiler may use the StringBuffer class or a
similar technique to reduce the number of intermediate String objects
that are created by evaluation of an expression.

For primitive types, an implementation may also optimize away the
creation of a wrapper object by converting directly from a primitive
type to a string.

See language specifications here.

TL;DR

  • Operator precedence for + is from left to right
  • If any operand in a binary operation is a String, the result is a String
  • If both operands are numbers, the result is a number

More Related Contents:

  1. StringBuilder vs String concatenation in toString() in Java
  2. How can I concatenate two arrays in Java?
  3. Concatenating null strings in Java [duplicate]
  4. String concatenation: concat() vs “+” operator
  5. Is it better practice to use String.format over string Concatenation in Java?
  6. The concatenation of chars to form a string gives different results
  7. Java: String concat vs StringBuilder – optimised, so what should I do?
  8. How to parse a mathematical expression given as a string and return a number? [duplicate]
  9. Regex to match a C-style multiline comment
  10. Convert float to String and String to float in Java
  11. How to split a string in Java
  12. Get variable by name from a String
  13. Java – Best way to grab ALL Strings between two Strings? (regex?)
  14. Fast algorithm for searching for substrings in a string
  15. Extracting pairs of words using String.split()
  16. XML Document to String
  17. String replace a Backslash
  18. Converting ArrayList of Characters to a String?
  19. Java String literals concatenation
  20. Can a valid Unicode string contain FFFF? Is Java/CharacterIterator broken?
  21. Display special characters using System.out.println
  22. How do I find out if first character of a string is a number?
  23. In Java, how to find if first character in a string is upper case without regex
  24. How to convert String object to Boolean Object?
  25. Sort a single String in Java
  26. Java string intern and literal
  27. Java split String performances
  28. Find all words with 3 letters with regex
  29. Is concatenating with an empty string to do a string conversion really that bad?
  30. Java replace all square brackets in a string

Leave a Comment