Groovy

Recently, I found that something called Groovy is getting popular. Then, I decided to have a look at it. Following are some notes I made during learning of Groovy.
In terms of underlying foundation, Groovy is identical to Java. They all rely on JVM. The advantage of Groovy is that it enhances Java so that programs can be written more compactly and more intuitively. First, Groovy looks like a dynamic script language which is quite different from traditional languages like Java. Users don't need to compile groovy files into .class files manually. Groovy compiler does this automatically for us when a program is executed. Besides, Groovy provides extensive support to make programming an easy job. For example, you can write code like this: mylist = [1, 3, 5]; mylist.each({it -> println it});

Collections:
(1) Range (http://groovy.codehaus.org/api/groovy/lang/Range.html)

Declaration: dot operator (..)
    (leftBound..rightBound)  inclusive(leftBound<= value <=rightBound)
    (leftBound..<rightBound) half-exclusive(leftBound<=value<rightBound)
Note: It is not necessary to let leftBound smaller than rightBound. Range can have a lower left bound and a higher right bound. It is called reverse range.
Declaration Samples:
    ('a'..'c') ('ab'..'az')
    new IntRange(0,10)
    (0..10).each({element -> println element})
Illegal samples:
    ('a'..'bc') ('ab'..'bc')
Data objects can be used in ranges. Unit of increase or decrease is one day.
Implementation:
    IntRange, EmptyRange, ObjectRange
Useful Functions:
    each
    contains
    isCase (used in switch statement. This has the same meaning as contains)
Usage:
(1)money = 10000
    switch(money){
        case 0..1000: taxRate = 0.1; break
        case 1001..5000: taxRate = 0.2; break
        default: taxRate = 0.3; break
    }
(2)payroll = [1000, 2000, 1004, 4000];
    filter = 2000..3000
    pryroll.grep(filter)
Customized Range:
Users can create their own types which can be used with ranges, provided following requirements are satisfied:
(1) The type implements functions previous and next.
(2) The type implements compareTo function by overriding the <=> spaceship operator.

(2) List

Declaration:bracket operator([item1, item2, item3])
Declaration Samples:
    list = [1, 2, 3]
    list2 = ['abc', 2, 'def']
Usage:
    println list[0]    //print 1
    println list[0..2] //print 1 2 3
    println list[0,1]  //print 1 2
    list2[3] = 10    //extend the list automatically, list2 becoms ['abc',2,'def',10]
    list2[0..2] = 100 //list2 becomes [100,10]
    list2[0..2] = [1 100] //list2 becoms [1, 100, 10]
Note: access indices can be negative numbers which count from the end of the list. For example: list[-1].

(3) Map

Closure
Closures are objects essentially.
Closures are mainly used to represent a specific behavior. In Java, an object has behavior as well as data.
If the closure needs only a single parameter, Groovy provides a default name --it. Print a file: new File('input.txt').eachLine{ println it }
Declaration:
    (1..10).each{ele -> println ele} or (1..10).each({ele -> println ele})
    def clo = {ele -> println ele}
    def Closure getClosure(){
        return { ele -> println ele }
    }
You can use methods as closures.
Call closures:
    closure(parameters)    or    closure.call(parameters)

Audio Record

Recently, I am looking for a good audio recording software.
In my English class, we use Sanako to do this job. It is easy to use, but I think it is too simple in terms of functionality. As a result, I wanted to find a free and great audio recording software. At last, I found one which I think satisfies my requirements. It is Audacity -- a open source software. It is powerful. It supports multi-tracks.
Chinese software:
(1) wavecn
    It looks like a great product. However, I have not tried it.

Some commercial software:
(1) Cooledit

Javascript snippet

In my application, I need to modify a select dynamically. I found out inconsistency between IE and Firefox. In Firefox, property innerHTML can be used to set the content of a select object while it does not work in IE.

Following snippet works in Firefox:

var ele = document.getElementById('select1');
var htm = '<option value="coke">cokecola</option><option value="pepsi">Pepsi</option>';
ele.innerHTML = htm;

But it does not work in IE. You should use following snippet in IE:

var ele = document.getElementById('select1');
ele.options[0] = new Option('cokecola', 'coke');
ele.options[1] = new Option('Pepsi', 'pepsi');