java linklist 遍历_Java LinkedList遍历的7种方法
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Java LinkedList遍历的7种方法
LinkedList遍历方法
1. 一般的for循环(随机访问)遍历
int size = list.size();
for (int i=0; i
list.get(i);
}
2. for--each循环遍历
for (Integer integ:list){
;
}
3. 迭代器iterator遍历
for(Iterator iter = list.iterator(); iter.hasNext();)
iter.next();
4. 用pollFirst()遍历
while(list.pollFirst() != null)
;
5. 用pollLast()遍历
while(list.pollLast() != null)
;
6. 用removeFirst()遍历
try {
while(list.removeFirst() != null)
;
} catch (NoSuchElementException e) {
}
7. 用removeLast()遍历
try {
while(list.removeLast() != null)
;
} catch (NoSuchElementException e) {
}
实例
public class LinkedListTest {
public static void main(String[] args) {
LinkedList llist = new LinkedList();
for (int i=0; i<100000; i++)
llist.addLast(i);
byCommonFor(llist) ;// 通过一般for循环来遍历LinkedList
byForEach(llist) ; // 通过for-each来遍历LinkedList
byIterator(llist) ; // 通过Iterator来遍历LinkedList
byPollFirst(llist) ; // 通过PollFirst()遍历LinkedList
byPollLast(llist) ; // 通过PollLast()遍历LinkedList
byRemoveFirst(llist) ; // 通过removeFirst()遍历LinkedList
byRemoveLast(llist) ; // 通过removeLast()遍历LinkedList
}
private static void byCommonFor(LinkedList list) {// 通过一般for循环来遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
int size = list.size();
for (int i=0; i
list.get(i);
}
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byCommonFor------->" + total+" ms");
}
private static void byForEach(LinkedList list) {// 通过for-each来遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
for (Integer integ:list)
;
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byForEach------->" + total+" ms");
}
private static void byIterator(LinkedList list) {// 通过Iterator来遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
for(Iterator iter = list.iterator(); iter.hasNext();)
iter.next();
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byIterator------->" + total+" ms");
}
private static void byPollFirst(LinkedList list) {//通过PollFirst()遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
while(list.pollFirst() != null)
;
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byPollFirst------->" + total+" ms");
}
private static void byPollLast(LinkedList list) {// 通过PollLast()遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
while(list.pollLast() != null)
;
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byPollLast------->" + total+" ms");
}
private static void byRemoveFirst(LinkedList list) {// 通过removeFirst()遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
try {
while(list.removeFirst() != null)
;
} catch (NoSuchElementException e) {
}
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byRemoveFirst------->" + total+" ms");
}
private static void byRemoveLast(LinkedList list) {// 通过removeLast()遍历LinkedList
if (list == null)
return ;
long start = System.currentTimeMillis();
try {
while(list.removeLast() != null)
;
} catch (NoSuchElementException e) {
}
long end = System.currentTimeMillis();
long total = end - start;
System.out.println("byRemoveLast------->" + total+" ms");
}
}
运行结果：
byCommonFor------->5342 ms
byForEach------->11 ms
byIterator------->8 ms
byPollFirst------->4 ms
byPollLast------->0 ms
byRemoveFirst------->0 ms
byRemoveLast------->0 ms
由此可见，遍历LinkedList时，使用removeFist()或removeLast()效率最高。但用它们遍历时，会删除原始数据；若单纯只读取，而不删除，LinkedList遍历时建议使用For-each或者迭代器的方式。千万不要通过随机访问去遍历LinkedList！
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