Cast primitive type array into object array in java
Here is a simple one-liner: Double[] objects = ArrayUtils.toObject(primitives); You will need to import Apache commons-lang3: import org.apache.commons.lang3.ArrayUtils;
primitive
Using int vs Integer
the Integer class is provided so that values can be boxed/unboxed in a pure OO manner. use int where appropriate unless you specifically need to use it in an OO way; in which case Integer is appropriate. Java Int vs Integer However, very different things are going on under the covers here. An int is … Read more
Comparing float and double primitives in Java
Take a look at What every computer scientist should know about floating point numbers. Squeezing infinitely many real numbers into a finite number of bits requires an approximate representation…. — Edit to show what the above quote means — You shouldn’t ever compare floats or doubles for equality; because, you can’t really guarantee that the … Read more
Overriding Default Primitive Type Handling in Json.Net
Unfortunately the method JsonReader.SetToken(JsonToken, Object, Boolean) is no longer virtual. In more recent versions of Json.NET (10.0.1 or later), one must override JsonReader.Read() and do the necessary conversion there, then update the reader’s value with the desired value type. For instance, if you would prefer your JsonTextReader to return Int32 instead of Int64 whenever possible, … Read more
What does int.class mean
A primitive becoming an Object For primitives, there are Class objects available as constants named TYPE in the corresponding wrapper classes — i.e. int.class is changed to java.lang.Integer.TYPE . For other types, the compiler creates a private member variable in the class being compiled to hold the Class object, and generates code to initialize that … Read more
Java storing two ints in a long
y is getting sign-extended in the first snippet, which would overwrite x with -1 whenever y < 0. In the second snippet, the cast to int is done before the shift, so x actually gets the value of y. long l = (((long)x) << 32) | (y & 0xffffffffL); int x = (int)(l >> 32); … Read more
Check type of primitive field
You’re using the wrong constant to check for Long primitives – use Long.TYPE, each other primitive type can be found with a similarly named constant on the wrapper. eg: Byte.TYPE, Character.TYPE, etc.
Which one to use, int or Integer
Integer is a better option, as it can handle null; for int, null would become 0, silently, if resultSet.getInt(..) is used. Otherwise, it might throw some exception, something like, “Unable to set null to a primitive property”. Performance is of little concern here. if you choose int, you will end-up adding extra handling code; and … Read more
How many primitives does it take to build a LISP machine? Ten, seven or five?
Basic Predicates/F-functions McCarthy‘s Elementary S-functions and Predicates were: atom Which was necessary because car and cdr are defined for lists only, which means you cannot count on any sort of answer to indicate what was happening if you gave car an atom. eq For testing equality between atoms. car For returning the first half (address) … Read more
Inconsistent behavior on java’s ==
Autoboxing of primitives into objects (as used in your calls to method uses a cache of small values. From the Java Language Specification section 5.1.7: If the value p being boxed is true, false, a byte, a char in the range \u0000 to \u007f, or an int or short number between -128 and 127, then … Read more