Java USES ArrayList traversal and efficiency comparison example analysis

This article illustrates Java's use of ArrayList traversal and efficiency comparisons. Share with you for your reference. The details are 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(" The first "+i+" a ");
}
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();
//Methods 3
for (String vv :arrL){
  arrLTmp3.add(vv);
}
long t4 = System.nanoTime();
//Methods 4
for(int i=0;i
  arrLTmp4.add(arrL.get(i));
}
long t5 = System.nanoTime();
System.out.println(" The first method is time-consuming: " + (t2-t1)/1000 + " microseconds ");
System.out.println(" The second method is time-consuming: " + (t3-t2)/1000 + " microseconds ");
System.out.println(" The third method is time-consuming: " + (t4-t3)/1000 + " microseconds ");
System.out.println(" The fourth method is time-consuming: " + (t5-t4)/1000 + " microseconds ");

Output results:

 The first method is time-consuming: 143069 microseconds 
 The second method is time-consuming: 381666 microseconds 
 The third method is time-consuming: 125909 microseconds 
 The fourth method is time-consuming: 63693 microseconds 

Change the above 1000000 to 10, and the output is:

 The first method is time-consuming: 307 microseconds 
 The second method is time-consuming: 14 microseconds 
 The third method is time-consuming: 14 microseconds 
 The fourth method is time-consuming: 14 microseconds 

I hope this article has been helpful to your Java programming.