C# List Note
http://allantech.blogspot.com/2007/03/performance-arraylist-vs-list.html
Array : array element can be of any type,including an array type , an array with n elements and
the "n" must be given a value.
List: List element can be a strongly typed list of objects that can be accessed by index.List with
elements can be any Length.
ArrayList : ArrayList element can be of any type,ArrayList with n elements can be any Length.
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Java arrayList Note
get(int) : Effective.
add(Object obj) : Effective.
set(int index,Object obj):Effective.
add(int index,Object obj):Low Effective.
remove(int index): Low Effective.
contains(Object obj):Low Effective.(Because Of Calling index Of)
Remove List Way:
1.Use Remove method,Delete Element.
2.Rebird new ArrayList,Insert Useless Element.
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Java Example
There is an ArrayList include Integer,We need to Delete odd number
public class Example
{
private static List exampleNew(int cnt)
{
List p = new ArrayList();
for(int i =0; i < cnt;i++)
p.Add(new Integer(i));
List o = new ArrayList(100);
for(int i = 0;i < p.Size();i++)
if(i%2==0)
o.Add(p.get(i));
return o;
}
private static List exampleRemove(int cnt)
{
List p = new List();
for(int i =0; i < cnt ; i++)
p.Add(new Integer(i));
for(int i = 0 ; i < p.Size();i++)
if(i%2 != 0 )
p.Remove(i);
return p;
}
public static void example(int total,int cnt)
{
double time01,time02;
time01 = System.currentTimeMillis();
for(int i =0; i < total / cnt; i ++)
exampleNew(cnt);
time02 = System.currentTimeMillis();
double time03 = time02-time01;
time01 = System.currentTimeMillis();
for(int i =0; i < total/cnt;i++)
exampleRemove(cnt);
time02 = System.currentTimeMillis();
double time04 = time02-time01
System.out.println("List Size : " + cnt);
System.out.println("using New List:" + time03+"ms");
System.out.println("using Remove:"+time04+"ms");
System.out.println("New ---- Remove" + time03/time04+ " :1");
}
public static void main(String[] args)
{
double time01,time02;
int total = 100*1000;
int cnt=1;
while(cnt <= total)
{
example(total,cnt);
cnt *=10;
}
}
}
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Result:
When ArrayList is equal or bigger then 1000,the effective will have big different,
therefore, Use Add Metod is greater then Remove Method.
