Java Note

1. get the length of array

    a. int[] num = {...};    int len = num.length;

    b. String s = "abcdefg";    int len2 = s.length();

    c. int[] nums = {{}， {}， {}}；    int len3 = nums.length;    int len4 = nums[0].length;

2. read in a set of numbers into an array

    BufferedReader in = new BufferedReader(new inputStreamReader(System in));

    String line;

    in = line.readLine();

    int[] prices = stringToIntegerArray(line);

3. find the max/min in an array

    a. stream

    b. collection

    c. sort

        code:

            int arr[] = {10, 5, 8};

            int min = Arrays.stream(arr).min().getAsInt();

            System.out.println(min);

            min = Collections.min(Arrays.asList(ArrayUtils.toObject(arr)));

            System.out.printIn(min);

            Array.sort(a);

            System.out.println(a[0]);

4.

trim()方法返回调用字符串对象的一个副本，但是所有起始和结尾的空格都被删除了，例子如下：String s="    Hello World      ".trim();
就是把"Hello World"放入s中。

5. String reverse

    String str = "Hello";

    a. str = new StringBuffer(str).reverse().toString();

    b. StringBuilder rev = new StringBuilder();

       for(int i = message.length() - 1; i >= 0; i--)

            rev.append(message.charAt(i));

            System.out.println(rev.toString());

6.