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Groovy Api Tutorial



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  • defhaha = "haha"def a = /asdasdas ${haha}/printlnhaha.getClass().nameprintlna.getClass().nameprintln "haha"[1..3]defnum = "012345678"printlnnum[-1 .. 0]for(str in 'abc'..'abz'){ print "$str "}


  • 1. Groovy API
    QIYI AD Team
    Yan Lei
  • 2. You can define a variable without specifying TYPE
    def user = new User()
    You can define function argumentswithout TYPE
    void testUser(user) { user.shout() }
    Types in Groovy
    1.1.getClass().name // java.math.BigDecimal
    Dynamic Type
  • 3. import java.util.*;
    public class UsingCollection
    public static void main(String[] args)
    ArrayList<String> lst = new ArrayList<String>();
    Collection<String> col = lst;
    lst.add("one" );
    lst.add("two" );
    lst.add("three" );
    System.out.println("Added three items, remove two, so 1 item to remain." );
    System.out.println("Number of elements is: " + lst.size());
    System.out.println("Number of elements is: " + col.size());
    Please Give Result running on Java & Groovy
  • 4. One of The biggest contributions of GDK is extending the JDK with methods that take closures.
    Define a closure
    def closure = { println “hello world”}
    defpickEven(n, block){
    for(inti = 2; i <= n; i += 2){
    pickEvent(10, {println it})=== pickEvent(10) {println it} when closure is the last argument
    def Total = 0; pickEvent(10) {total += it}; println total
    Using Closures
  • 5. When you curry( ) a closure, you’re asking the parameters to be prebound.
    Date date = new Date("11/15/2007" )
    postFortune= closure.curry(date)
    postFortune "Your day is filled with ceremony"
    postFortune "They're features, not bugs"
    tellFortunes() { date, fortune ->
    println"Fortune for ${date} is '${fortune}'"
    Curried Closure
  • 6. def examine(closure){
    println "$closure.maximumNumberOfParameters parameter(s) given:"
    for(aParameter in closure.parameterTypes) { println }
    examine() { } // 1, Object
    examine() { it } // 1, Object
    examine() {-> } // 0
    examine() { val1 -> } // 1, Object
    examine() {Date val1 -> } // 1, Date
    examine() {Date val1, val2 -> } // 2, Date, Object
    examine() {Date val1, String val2 -> } // 2, Date, String
    Dynamic Closures
  • 7. Three properties of a closure determine which object handles a method call from within a closure. These are this, owner, and delegate. Generally, the delegate is set to owner, but changing it allows you to exploit Groovy for some really good metaprogramming capabilities.
    Example ???
    Closure Delegation
  • 8. Creating String with ‘, “(GStringImpl), ‘’’(multiLine)
    getSubString using [] , “hello”[3], “hello”[1..3]
    As String in Java, String in Groovy is immutable.
    Working with String
  • 9. Problem
    price = 568.23
    company = 'Google'
    quote = "Today $company stock closed at $price"
    println quote
    stocks = [Apple : 130.01, Microsoft : 35.95]
    stocks.each { key, value ->
    company = key
    price = value
    println quote
    Why ?
    When you defined the GString—quote—you bound the variables company and price to a String holding the value Google and an Integer holding that obscene stock price, respectively. You can change the company and price references all you want (both of these are referring to immutable objects) to refer to other objects, but you’re not changing what the GString instance has been bound to.
    Using closure
    quote = “Today ${->company} stock closed at ${->price}”
    GString Lazy Evaluation Problem
  • 10. “hello world” -= “world”
    for(str in ‘abc’..’abz’){ print “${str} ”}
    Regular Expressions
    Define pattern : def pattern = ~”[aAbB]”
    =~ , ==~
    “Groovy is good” =~ /g|Groovy/ //match
    “Groovy is good” ==~ /g|Groovy/ //no match
    ('Groovy is groovy, really groovy'=~ /groovy/).replaceAll(‘good' )
    String Convenience Methods
  • 11. def a = [1,2,3,4,5,6,7] // ArrayList
    Def b = a[2..5] // b is an object of RandomAccessSubList
    Using each for iterating over an list
    a.each { println it }
    Finder Methords: find & findAll
    a.find {it > 6} //7 return the first match result
    a.findAll {it > 5} //[5,7] return a list include all matched members
    Convenience Method
  • 12. def a = [s:1,d:2,f:3] //LinkedHashMap
    fetch value by Key: a.s, a[“s”]
    a.each {entry -> println “$entry.key : $entry.value” }
    a.each{key, value -> println“$key : $value” }
    Collect, find, findAll
    Any, every
  • 13. The dump and inspect Methods
    dump( ) lets you take a peek into an object.
    java.lang.String@5e918d2 value=[h, e, l, l, o] offset=0 count=5 hash=99162322
    Groovy also adds another method, inspect( ), to Object. This method is intended to tell you what input would be needed to create an object. If unimplemented on a class, it simply returns what toString( ) returns. If your object takes extensive input, this method will help users of your class figure out at runtime what input they should provide.
    Object Extensions
  • 14. identity: The Context Method
    lst = [1, 2]
    lst.identity {
    println size() //4
    println contains(2) // true
    println "this is ${this}," //this is Identity@ce56f8,
    println "owner is ${owner}," //owner is Identity@ce56f8,
    println "delegate is ${delegate}." //delegate is [1, 2, 3, 4].
    Object Extensions
  • 15. Sleep: suppresses the Interrupted-Exception.
    If you do care to be interrupted, you don’t have to endure try-catch. Instead, in Groovy, you can use a variation of the previous sleep( ) method that accepts a closure to handle the interruption.
    new Object().sleep(2000) {
    println "Interrupted... " + it
    flag //if false, the thread will sleep 2 second as if there is no interruption
    Object Extensions
  • 16. class Car{
    int miles, fuelLevel
    void run(){println “boom …”}
    Void status(int a, String b) {println“$a --- $b”}
    car = new Car(fuelLevel: 80, miles: 25)
    Indirect Property Access
    println car[“miles”]
    Indirect Method Invoke
    car.invokeMethod(“status”, [1,”a”] as Object[])
    Object Extensions
  • 17. Overloaded operators for Character, Integer, and so on. Such as plus( ) for operator +, next( ) for operator++, and so on.
    Number (which Integer and Double extend) has picked up the iterator methods upto( ) and downto( ). It also has the step( ) method.
    Thread.start{} & Thread.startDaemon()
    java.lang extensions
  • 18. Read file
    println new File('thoreau.txt' ).text
    new File('thoreau.txt' ).eachLine { line ->println line}
    println new File('thoreau.txt' ).filterLine { it =~ /life/ }
    Write file
    new File("output.txt" ).withWriter{ file ->
    file << "some data..."
    } Extensions
  • 19. Details about calling a method
    Groovy Object
  • 20. Use MetaClass to modify a class at runtime
    Dynamic Adding or modifying Method
    A.metaclass.newMethod= { println “new method”}
    Dynamic Adding or modifying variable
    A.metaClass.newParam = 1
    After these, U can
    new A().newMethod()
    println new A().newParam
  • 21. Implements GroovyInterceptable & define method invokeMethod(String name, args)
    Using MetaClass
    define a closure for metaclass
    Car.metaClass.invokeMethod = { String name, args->
    Intercepting Methods