primitive

I need to create a data transfer object, which I will use for storing the records retrieved from database. In this data transfer object, I need to declare a numeric field. For that which one is better - int or Integer If I am defining the field as Integer, will there be any performance impact because of 'Integer' type if I am going to retrieve more than 2000 records from DB!? Thanks in advance. 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

On this site they say there are 10 LISP primitives. The primitives are: atom, quote, eq, car, cdr, cons, cond, lambda, label, apply . http://hyperpolyglot.wikidot.com/lisp#ten-primitives Stevey reckons there are seven (or five): Its part of the purity of the idea of LISP: you only need the seven (or is it five?) primitives to build the full machine. http://steve-yegge.blogspot.com/2006/04/lisp-is-not-acceptable-lisp.html What is the minimum number of primitives to build a LISP machine (ie something that can run an eval/value function on LISP code)? (And which ones are they?) (I can understand

Consider this code: class test { public static void main(String[] args) { test inst_test = new test(); int i1 = 2000; int i2 = 2000; int i3 = 2; int i4 = 2; Integer Ithree = new Integer(2); // 1 Integer Ifour = new Integer(2); // 2 System.out.println( Ithree == Ifour ); inst_test.method( i3 , i4 ); inst_test.method( i1 , i2 ); } public void method( Integer i , Integer eye ) { System.out.println(i == eye ); } } It prints: false true false I understand the first false , the == operator only checks if two references are working on the same object, which in this case aren't. The following true and

Specifically, with a SortedMap<Vector<String>, int> I get "dimensions expected after this ( int ) token." Help! No, this is not possible. Use Integer instead. Autoboxing takes care of the rest (i.e. for most purposes you can program as if you had actually used int because Java converts to and from Integer automatically for you). Konrad is correct. Alternately, you can use the trove class TObjectIntHashMap to map Objects to primitive ints. 来源： https://stackoverflow.com/questions/414408/is-it-possible-to-use-a-primitive-type-int-in-as-a-generic-type-in-java

I came across a class using Integer variables to capture size to be used in a for loop. Is this good practice or should we use the int primitive data type? Integer size = something.getFields().size(); for (Integer j = 0; j < size - 1; ++j) 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 a number; an > Integer is a pointer that can reference an

I came across a strange corner of Java.(It seems strange to me) double dd = 3.5; float ff = 3.5f; System.out.println(dd==ff); o/p: true double dd = 3.2; float ff = 3.2f; System.out.println(dd==ff); o/p: false I observed that if we compare any two values (a float and a double as I mentioned in the example) with .5 OR .0 like 3.5, 234.5, 645.0 then output is true i.e. two values are equal otherwise output is false though they are equals. Even I tried to make method strictfp but no luck. Am I missing out on something. Take a look at What every computer scientist should know about floating point

I am trying to test the speed of autoboxing and unboxing in Java, but when I try to compare it against an empty loop on a primitive, I noticed one curious thing. This snippet: for (int j = 0; j < 10; j++) { long t = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) ; t = System.currentTimeMillis() - t; System.out.print(t + " "); } Every time I run this, it returns the same result: 6 7 0 0 0 0 0 0 0 0 Why does the first two loops always take some time, then the rest just seem to be skipped by the system? In this answer to this post, it is said that Just-In-Time compilation will be