1 例項測試程式碼

<pre name="code" class="java">        // 1 ArrayList set sort elements and list elements
	public static void printArrList() {
		List<String> listLined = new ArrayList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < 1000000; x++) {
			listLined.add(String.valueOf(x));
		} 
		for (int m = 0; m < listLined.size(); m++) {
			String tempString = listLined.get(m);
		}
		long st4 = System.currentTimeMillis();
		System.out.println("arrayList Get Elements time By normal =" + (st4 - st3));
	}

	// 2 LinedkList set sort elements and list elements
	public static void printLinkedList() {
		List<String> listLined = new LinkedList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < <span style="color:#FF0000;">100000</span>; x++) {
			listLined.add(String.valueOf(x));
		} 
		for (int m = 0; m < listLined.size(); m++) {
			String tempString = listLined.get(m);
		}
		long st4 = System.currentTimeMillis();
		System.out.println("LinkedList Get Elements time  By normal =" + (st4 - st3)); 
	}

	// 3 ArrayList set sort elements and list elements By FOR
	public static void printArrListByFor() {
		List<String> listLined = new ArrayList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < 1000000; x++) {
			listLined.add(String.valueOf(x));
		} 
		for (String m : listLined) {
			String tempString = m;
		}
		long st4 = System.currentTimeMillis();
		System.out.println("arrayList Get Elements By FOR  with time="
				+ (st4 - st3));
	}

	// 4 LinkedList set sort elements and list elements By FOR
	public static void printLinkedListByFor() {
		List<String> listLined = new LinkedList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < 1000000; x++) {
			listLined.add(String.valueOf(x));
		} 
		for (String m : listLined) {
			String tempString = m;
		}
		long st4 = System.currentTimeMillis();
		System.out.println("LinkedList Get Elements By FOR  with time="
				+ (st4 - st3));
	}

	// 5 ArrayList set sort elements and list elements By Itorator
	public static void printArrListByItorator() {
		List<String> listLined = new ArrayList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < 1000000; x++) {
			listLined.add(String.valueOf(x));
		} 
		Iterator<String> iterator = listLined.iterator();
		while( iterator.hasNext() ){ 
			String tempString = iterator.next();
		}
		long st4 = System.currentTimeMillis();
		System.out.println("arrayList Get Elements By Itorator  with time="
				+ (st4 - st3));
	}

	// 6 LinkedList set sort elements and list elements By Itorator
	public static void printLinkedListByItorator() {
		List<String> listLined = new LinkedList<String>(); 
		long st3 = System.currentTimeMillis();
		for (int x = 0; x < 1000000; x++) {
			listLined.add(String.valueOf(x));
		} 
		Iterator<String> iterator = listLined.iterator();
		while( iterator.hasNext() ){ 
			String tempString = iterator.next();
		}
		long st4 = System.currentTimeMillis();
		System.out.println("LinkedList Get Elements By Itorator  with time="
				+ (st4 - st3));
	}

	public static void main(String[] args) {
		for(int x = 1; x <= 5 ; x++ ){
                  System.out.println(" loop test time:" + x);
		printArrList();
			printLinkedList();
			printArrListByFor();
			printLinkedListByFor();
			printArrListByItorator();
			printLinkedListByItorator();
		}
	}
 

2   3次輸出結果

<pre name="code" class="java">loop test time:1
arrayList Get Elements time By normal =184
LinkedList Get Elements time  By normal =7434
arrayList Get Elements By FOR  with time=218
LinkedList Get Elements By FOR  with time=138
arrayList Get Elements By Itorator  with time=231
LinkedList Get Elements By Itorator  with time=92

 loop test time:2
arrayList Get Elements time By normal =98
LinkedList Get Elements time  By normal =7428
arrayList Get Elements By FOR  with time=185
LinkedList Get Elements By FOR  with time=62
arrayList Get Elements By Itorator  with time=92
LinkedList Get Elements By Itorator  with time=180

 loop test time:3
arrayList Get Elements time By normal =43
LinkedList Get Elements time  By normal =8004
arrayList Get Elements By FOR  with time=104
LinkedList Get Elements By FOR  with time=64
arrayList Get Elements By Itorator  with time=76
LinkedList Get Elements By Itorator  with time=51

 loop test time:4
arrayList Get Elements time By normal =47
LinkedList Get Elements time  By normal =7490
arrayList Get Elements By FOR  with time=109
LinkedList Get Elements By FOR  with time=64
arrayList Get Elements By Itorator  with time=99
LinkedList Get Elements By Itorator  with time=65
 loop test time:5
arrayList Get Elements time By normal =62
LinkedList Get Elements time  By normal =7890
arrayList Get Elements By FOR  with time=44
LinkedList Get Elements By FOR  with time=57
arrayList Get Elements By Itorator  with time=84
LinkedList Get Elements By Itorator  with time=49
 

             2 printLinkedList()方法只能處於十萬級別量, printLinkedListByItorator（）只能處於百萬量級別，千萬量級別會報：java.lang.OutOfMemoryError: Java heap space

3 結論

1. ArrayList是實現了基於動態陣列的資料結構，LinkedList基於連結串列的資料結構。

 2. 對於隨機訪問get和set，ArrayList覺得優於LinkedList，因為LinkedList要移動指標。

 3. 對於新增和刪除操作add和remove，LinedList比較佔優勢，因為ArrayList要移動資料 ，但在尾部新增和刪除除外。

4. For（foreach)、Iterator原理都是基於迭代器，區別不大，在獲取元素的時候的時間複雜度是 O(1) （使用了 getNext() 和 hasNext() 方法），最終的時間複雜度為 O(n), 並且兩者有迭代器的記憶體開銷;
    而LinkedList迴圈裡每次在呼叫 get(i) 的時候花費的時間複雜度為 O(n)，最終整個迴圈的時間複雜度就是 O(n^2);
        ArrayList迴圈裡每次在呼叫  get(i) 方法的時間複雜度就是 O(1)，最終整個迴圈的時間複雜度就是 O(n);

4 建議

  如果不考慮記憶體空間：使用普通的ArrayList 的Iterator 方法遍歷，為最優方案

  考慮記憶體空間：使用普通的ArrayList，並for遍歷為最優方案