The Java Language Specification, Third Edition

LEXICAL STRUCTURE String Literals 3.10.5
generally, strings that are the values of constant expressions (§15.28)—are
“interned” so as to share unique instances, using the method String.intern.
Thus, the test program consisting of the compilation unit (§7.3):
package testPackage;
class Test {
public static void main(String[] args) {
String hello = "Hello", lo = "lo";
System.out.print((hello == "Hello") + " ");
System.out.print((Other.hello == hello) + " ");
System.out.print((other.Other.hello == hello) + " ");
System.out.print((hello == ("Hel"+"lo")) + " ");
System.out.print((hello == ("Hel"+lo)) + " ");
System.out.println(hello == ("Hel"+lo).intern());
}
}
class Other { static String hello = "Hello"; }
and the compilation unit:
package other;
public class Other { static String hello = "Hello"; }
produces the output:
true true true true false true
This example illustrates six points:
• Literal strings within the same class (§8) in the same package (§7) represent
references to the same String object (§4.3.1).
• Literal strings within different classes in the same package represent references
to the same String object.
• Literal strings within different classes in different packages likewise represent
references to the same String object.
• Strings computed by constant expressions (§15.28) are computed at compile
time and then treated as if they were literals.
• Strings computed by concatenation at run time are newly created and therefore
distinct.
The result of explicitly interning a computed string is the same string as any
pre-existing literal string with the same contents.
DRAFT
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