A case study of Java using ArrayList traversal and efficiency comparison _java

This article describes the Java use of ArrayList traversal and efficiency comparisons. Share to everyone for your reference. Specifically as follows:

ArrayList ARRL = new ArrayList ();
ArrayList arrLTmp1 = new ArrayList ();
ArrayList arrLTmp2 = new ArrayList ();
ArrayList ArrLTmp3 = new ArrayList ();
ArrayList arrLTmp4 = new ArrayList ();
for (int i=0;i<1000000;i++) {
  arrl.add ("+i+");
}
Long T1 = System.nanotime ();
Method 1
Iterator it = Arrl.iterator ();
while (It.hasnext ()) {
  Arrltmp1.add (It.next ());
}
Long t2 = System.nanotime ();
Method 2 for
(iterator it2 = Arrl.iterator (); It2.hasnext ();) {arrltmp2.add () (
  it2.next ());
long t3 = System.nanotime ();
Method 3 for
(String vv:arrl) {
  arrltmp3.add (vv);
}
long T4 = System.nanotime ();
Method 4 for
(int i=0;i
  arrltmp4.add (Arrl.get (i));
}
Long T5 = System.nanotime ();
System.out.println ("First method time consuming:" + (T2-T1)/1000 + "microsecond");
System.out.println ("second method time consuming:" + (T3-T2)/1000 + "microsecond");
System.out.println ("Third method time consuming:" + (T4-T3)/1000 + "microsecond");
System.out.println ("Fourth method time consuming:" + (T5-T4)/1000 + "microsecond");

Output results:

The first method takes time: 143069 microseconds the
second method takes time: 381666 microseconds the
third method takes time: 125909 microseconds the
fourth method takes time: 63693 microseconds

Change the above 1000000 to 10 and the output is:

The first method takes time: 307 microseconds The
second method takes time: 14 microseconds the
third method takes time: 14 microseconds The
fourth method takes time: 14 microseconds

I hope this article will help you with your Java programming.