Every compile-time constant expression that is of type String will be put into the String pool. Essentially that means: if the compiler can (easily) “calculate” the value of the String without running the program, then it will be put into the pool (the rules are slightly more complicated than that and have a few corner … Read more
This is a technique to ensure that CONSTANT is not actually a constant. When the Java compiler sees a reference to a final static primitive or String, it inserts the actual value of that constant into the class that uses it. If you then change the constant value in the defining class but don’t recompile … Read more
Yes. In general any literal string, identifier, or other constant string in JS source is interned. However implementation details (exactly what is interned for instance) varies, as well as when the interning occurs. Note that a string value is not the same as a String Object though, String Objects are not interned because that would … Read more
It seems that JDK7 process intern in a different way as before. I tested it with build 1.7.0-b147 and got “both are equal”, but when executing it (same bytecode) with 1,6.0_24 I do not get the message. It also depends where the String b2 =… line is located in the source code. The following code … Read more
In general, interning is something that just happens, automatically, when you use literal string values. Interning provides the benefit of only having one copy of the literal in memory, no matter how often it’s used. That being said, it’s rare that there is a reason to intern your own strings that are generated at runtime, … Read more
This is not undefined behavior, but unspecified behavior. For string literals, The compiler is allowed, but not required, to combine storage for equal or overlapping string literals. That means that identical string literals may or may not compare equal when compared by pointer. That means the result of A == B might be true or … Read more
This is implementation-specific, but your interpreter is probably interning compile-time constants but not the results of run-time expressions. In what follows CPython 3.9.0+ is used. In the second example, the expression “strin”+”g” is evaluated at compile time, and is replaced with “string”. This makes the first two examples behave the same. If we examine the … Read more
Java automatically interns String literals. This means that in many cases, the == operator appears to work for Strings in the same way that it does for ints or other primitive values. Since interning is automatic for String literals, the intern() method is to be used on Strings constructed with new String() Using your example: … Read more
http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#intern() Basically doing String.intern() on a series of strings will ensure that all strings having same contents share same memory. So if you have list of names where ‘john’ appears 1000 times, by interning you ensure only one ‘john’ is actually allocated memory. This can be useful to reduce memory requirements of your program. But … Read more