(aa.equals(ab)) // must use equals for equality checkī2=44 // between -128 to 127 it will work (aa=ab) // no cache for out of range values (b2=b3) // no cache for out of range values Long cache will only keep a static array of objects who's value is between -128 to 127 range inclusive so if your number is outside this range then you won't be able to use = operator for equality check (you don't believe, try following example) About Long.valueOf returning a direct Wrapper object without creating new Long object is a false statement, as according to internally use of Long.parseLong (which returns a primitive long), the primitive output of Long.parseLong will be converted to Wrapper object using by creating new object of Long class hence you wanna use direct Boxing or can call Long.valueOf=>Long.parseLong=>new LongĪ little more about caching(if pass value is long) :Ĭache is little helpful when you want to use = for equality check (like intern strings) with Object type.Public static Long valueOf(String s) throws NumberFormatException internally calls to Long.valueOf when you pass string **In other words, this method returns a Long object equal to the value of:** The result is a Long object that represents the integer value specified by the string. The argument is interpreted as representing a signed decimal long, exactly as if the argument were given to the parseLong() method. Returns a Long object holding the value of the specified String. official docs and the source code link (why don't use Byte instead of Long then because cache won't save every long value even this range apply for Integers too)įrom official docs public static Long valueOf(String s)

As about caching, this will work when your input is only between -128 to 127 (see the Example below) so it's up to the coder that you want to call Long.parseLong directly or through Long.valueOf when your object is of String type.(obviously, use direct call).

Every other function i.e Long.valueOf, Long(string) relies on Long.parseLong method which works as a core method for every String to Long conversion.

I would like to suggest using Long.parseLong over every other option because : The constructor creates a new objectĮach time it’s called, while the static factory method is never

For example, the static factory methodīoolean.valueOf(String) is almost always preferable to theĬonstructor Boolean(String). You can often avoid creating unnecessary objects by using staticįactory methods (Item 1) in preference to constructors on immutableĬlasses that provide both. since most of them reuse instances whenever it is possible making them potentially more efficient in term of memory footprint than the corresponding parse methods or constructors.Įxcerpt from Effective Java Item 1 written by Joshua Bloch: Generally speaking, it is a good practice to use the static factory method valueOf(str) of a wrapper class like Integer, Boolean, Long. To cache values within a particular range. Note that unlike theĬorresponding method in the Integer class, this method is not required Likely to yield significantly better space and time performance byĬaching frequently requested values.

Used in preference to the constructor Long(long), as this method is New Long instance is not required, this method should generally be Returns a Long instance representing the specified long value. The best approach is Long.valueOf(str) as it relies on Long.valueOf(long) which uses an internal cache making it more efficient since it will reuse if needed the cached instances of Long going from -128 to 127 included.

Calcite convert string to long