I am trying to concatenate strings in Java. Why isn't this working?
public class StackOverflowTest {
public static void main(String args[]) {
int theNumber = 42;
System.out.println("Your number is " . theNumber . "!");
}
}
views:
233answers:
9OK, thank you! :)
Dan
2010-09-20 17:49:48
+10
A:
You can concatenate Strings using the + operator:
System.out.println("Your number is " + theNumber + "!");
theNumber is implicitly converted to the String "42".
Peter Lang
2010-09-20 17:31:05
+4
A:
The concatenation operator in java is +, not .
Read this (including all subsections) before you start. Of try to stop thinking the php way ;)
To broaden your view on using strings in Java - the + operator for strings is actually transformed (by the compiler) into something similar to:
new StringBuilder().append("firstString").append("secondString").toString()
Bozho
2010-09-20 17:31:30
@Erick Robertson you are wrong. Reread the javadoc of `java.lang.String`. Using `+` is inefficient inside a loop. Otherwise the compiler uses `StringBuilder`
Bozho
2010-09-20 17:48:19
@Bozho: Wow, this is new to me. It wasn't always like this. I will stop explicitly using `StringBuilder` now when I can do the same thing with a sequence of `+`'s. I will still use it when concatenating strings across multiple lines, however, like when strings are being conditionally appended and such. Thank you!
Erick Robertson
2010-09-20 18:21:39
A:
You must be a PHP programmer.
Use a + sign.
"Your number is " + theNumber + "!"
Ed Manet
2010-09-20 17:31:31
+1
A:
This should work
public class StackOverflowTest
{
public static void main(String args[])
{
int theNumber = 42;
System.out.println("Your number is " + theNumber + "!");
}
}
Bragboy
2010-09-20 17:32:30
A:
"+" not "."
But be careful with String concatenation. Here's a link introducing some thoughts from IBM DeveloperWorks.
JohnMetta
2010-09-20 17:33:52
A:
There are two basic answers to this question: 1. [simple and inefficient] Use the + operator (string concatination).
"your number is" + theNumber + "!" (as noted elsewhere) 2. [less simple and less inefficient]: Use StringBuilder (or StringBuffer).
StringBuilder value;
value.append("your number is");
value.append(theNumber);
value.append("!");
value.toString();
I recommend against stacking operations like this:
new StringBuilder().append("I").append("like to write").append("confusing code");
Spaceisavaluablecommodity,asthissentancedemonstrates.
dwb
2010-09-20 17:56:21
JavaC converts "+" to use StringBuilders please see http://stackoverflow.com/questions/1532461/stringbuilder-vs-string-concatenation-in-tostring-in-java
ArtB
2010-09-20 18:20:33