ArrayList remove method -


i have @ arraylist source code，found remove method follows：

  /**  * removes element @ specified position in list.  * shifts subsequent elements left (subtracts 1  * indices).  *  * @param index index of element removed  * @return element removed list  * @throws indexoutofboundsexception {@inheritdoc}  */ public e remove(int index) {     if (index >= size)         throw new indexoutofboundsexception(outofboundsmsg(index));      modcount++;     e oldvalue = (e) elementdata[index];      int nummoved = size - index - 1;     if (nummoved > 0)         system.arraycopy(elementdata, index+1, elementdata, index,                          nummoved);     elementdata[--size] = null; // clear let gc work      return oldvalue; }

why doesn't consider situation when index<0?

passing in negative index fail on following line:

e oldvalue = (e) elementdata[index];

specifically, access elementdata underlying array happen negative index. cause arrayindexoutofboundsexception thrown, documentation describes:

thrown indicate array has been accessed illegal index. index either negative or greater or equal size of array.

hence, arraylist#remove() implementation not need language handle case of negative indices.

however, might wondering why code does make following check if index larger size:

 if (index >= size)     throw new indexoutofboundsexception(outofboundsmsg(index));

the reason check made because possible index passed in within bounds of elementdata larger logical size of actual list/array. in other words, size of underlying array not (and not) need in lock step actual number of entries in list. rather, jvm grow or shrink elementdata array needed depending size , usage of list.


Comments

Post a Comment

Popular posts from this blog

inversion of control - Autofac named registration constructor injection -

does autofac support specifying registration name in components' constructors? example: ninject's namedattribute . you need use autofac.extras.attributed package on top achieve this so let's have 1 interface , 2 classes: public interface ihello { string sayhello(); } public class englishhello : ihello { public string sayhello() { return "hello"; } } public class frenchhello : ihello { public string sayhello() { return "bonjour"; } } then have consumer class, in want select instance injected: public class helloconsumer { private readonly ihello helloservice; public helloconsumer([withkey("en")] ihello helloservice) { if (helloservice == null) { throw new argumentnullexception("helloservice"); } this.helloservice = helloservice; } public string sayhello() { return this.helloservice.sayhello()...
Read more

ios - Change Storyboard View using Seague -

i have following code checks connection server, , depending on want change views if no connection found. nsstring *connect = [nsstring stringwithcontentsofurl:[nsurl urlwithstring:@"http://myserver.com"] encoding:nsutf8stringencoding error:nil]; if (connect == null) { [self performseguewithidentifier:@"network_failure" sender:self]; } else { // other code here } my problem not change views. have added storyboard segue between 2 views identifier of network_failure . not have navigation controller or that, problem? thanks help! no not problem. first of all, in objectivec exists nil object oriented null . must use that. so: if(connect == nil) or better: if(!connect) so due fact nil not same of null , probably code does't enter in if scope . you have been able discover breakpoint. anyway: be sure set trigger segue (line) 2 view controller , , name network_failure (that not best name. should instead view1toview2 ) as, m...
Read more

verilog - Systemverilog dynamic casting issues -

i've code snippet following in testbench function void write_to_port( my_data_type_base data ); my_data_type_extended data_ext; if(!$cast(data_ext, data)); `uvm_error(get_type_name(), "failed cast"); `uvm_info(get_name(), $psprintf("data_ext :\n%s", data_ext.sprint()), uvm_medium) // write data_ext out port.... endfunction when run it, i'm getting uvm_error "failed cast." i'm not quire sure why $cast not returning 1. can see, i'm printing out extended class data item after casting uvm_info. can see it's being cast properly. if don't use $cast if condition, don't runtime error. isn't coding practice use if dynamic cast check if $cast returning 1 ? what might reason behind cast not returning 1 in above case? i think semicolon on line 'if' not belong? i think consumes if statement, , uvm_error executes regardless of how if evaluates: if(!$cast(data_ext, data)); <- no semico...
Read more