“我從真正有用的開始怎麼樣？你現在會看到 ArrayList 和泛型可以使用的幾種方法：”

“示例 1：”

從鍵盤讀取數字列表 
public static void main(String[] args) throws IOException
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in) );
    ArrayList<Integer> list = new ArrayList<Integer>() ;

    while (true)
    {
        String s = reader.readLine();
        if (s.isEmpty()) break;
        list.add(Integer.parseInt(s));
    }
}

“示例 2：”

與上面相同，但偶數被添加到列表的末尾，奇數被添加到它的開頭。 
public static void main(String[] args) throws IOException
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    ArrayList<Integer> list = new ArrayList<Integer>();

    while (true)
    {
        String s = reader.readLine();
        if (s.isEmpty()) break;

        int x = Integer.parseInt(s);
        if (x % 2 == 0)  // Check that the remainder is zero when we divide by two
            list.add(x);         // Add to the end
        else
            list.add(0, x);      // Add to the beginning
    }
}
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“示例 3：”

刪除所有大於 5 的數字： 
public static void main(String[] args) throws IOException
{
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in) );
    ArrayList<Integer> list = new ArrayList<Integer>();

    list.add(1);
    list.add(7);
    list.add(11);
    list.add(3);
    list.add(15);

    for (int i = 0; i < list.size(); ) // We moved the statement that increases i to inside the loop
    {
        if (list.get(i) > 5)
            list.remove(i);  // Don’t increase i if we deleted the current element
        else
            i++;
    }
}

“示例 4：”

將一個數組分成兩部分——偶數和奇數 
public static void main(String[] args) throws IOException
{
    // Static initialization of the array
    int[] data = {1, 5, 6, 11, 3, 15, 7, 8};

    // Create a list where all elements are Integers
    ArrayList&ltInteger> list = new ArrayList&ltInteger> ();

    // Use the array to fill the list
    for (int i = 0; i < data.length; i++) list.add(data[i]);

    ArrayList&ltInteger> even = new ArrayList&ltInteger>();  // Even numbers
    ArrayList&ltInteger> odd = new ArrayList&ltInteger>();    // Odd numbers

    for (int i = 0; i < list.size(); i++)
    {
        Integer x = list.get(i);
        if (x % 2 == 0)    // If x is even
            even.add(x);   // Add x to the collection of even numbers
        else
            odd.add(x);    // Add x to the collection of odd numbers
    }
}
2
任務
Java Syntax,  等級 7,  課堂 8
上鎖
Code entry
Your attention, please! Now recruiting code entry personnel for CodeGym. So turn up your focus, let your fingers relax, read the code, and then... type it into the appropriate box. Code entry is far from a useless exercise, though it might seem so at first glance: it allows a beginner to get used to and remember syntax (modern IDEs seldom make this possible).

“示例 5：”

合併列表 
public static void main(String[] args) throws IOException
{
    ArrayList<Integer> list1 = new ArrayList<Integer>();   // Create a list
    Collections.addAll(list1, 1, 5, 6, 11, 3, 15, 7, 8);   // Fill the list

    ArrayList<Integer> list2 = new ArrayList<Integer>();
    Collections.addAll(list2, 1, 8, 6, 21, 53, 5, 67, 18);

    ArrayList<Integer> result = new ArrayList<Integer>();

    result.addAll(list1);   // Add all values from each list to the new list
    result.addAll(list2);

    for (Integer x : result)   // A fast way to loop over all elements, only for collections
    {
        System.out.println(x);
    }
}

“太棒了！迭戈現在可以給我一卡車類似的練習嗎？”

“他會的。”