Groovy 学习笔记 (二)

 

1. == 是判断是否 equals, 而判断是否是同一对象则用 is

 

2. list 和 map 的一些方法：

 

def x  = 1..10

assert x.contains(5)

assert x.contains(15) == false

assert x.size()    == 10

assert x.from      == 1

assert x.to        == 10

assert x.reverse() == 10..1

 

3. 以下对象都有 size() 方法

Array, String, StringBuffer, Collection, Map, File

 

4. 数据类型：12 – Integer, 100L – Long, 1.23F – Float, 1.23D – Double, 123G – BigInteger, 1.23,1.23G – BigDecimal

 

如果一个小数, 末尾什么字符都没加, 那么这个小数使用的是 BigDecimal.

 

5. 操作符重载

Operator	Name	Method	Works with
a + b	Plus	a.plus(b)	Number,string,collection
a – b	Minus	a.minus(b)	Number,string,collection
a * b	Star	a.multiply(b)	Number,string,collection
a / b	Divide	a.div(b)	Number
a % b	Modulo	a.mod(b)	Integral number
a++	Post increment	a.next()	Number,string,range
++a	Pre increment
a–	Post decrement	a.previous()	Number,string,range
–a	Pre decrement
a**b	Power	a.power(b)	Number
a | b	Numerical or	a.or(b)	Integral number
a & b	Numerical and	a.and(b)	Integral number
a ^ b	Numerical xor	a.xor(b)	Integral number
~a	Bitwise complement	a.negate()	Integral number,string (the latter returning a regular expression pattern)
a[b]	Subscript	a.getAt(b)	Object,list,map,string、Array
a[b] = c	Subscript assignment	a.puAt(b,c)	Object,list,map,StringBuffer, Array
a << b	Left shift	a.leftShift(b)	Object, range, list, collection, pattern, closure; also used with collection c in c.grep(b), which returns all items of c where b.isCase(item)
a == b	Equals	a.equals(b)	Object, consider hashCode()
a != b	Not equals	!a.equals(b)	Object
a <=> b	Spaceship	a.compareTo(b)	java.lang.Comparable Any type
a > b	Greater than	a.compareTo(b) > 0
a >= b	Greater than or equal to	a.compareTo(b) >= 0
a < b	Less than	a.compareTo(b) < 0
a <= b	Less than or equal to	a.compareTo(b) <= 0
a as type	Enforced coercion	a.asType(typeClass)
a <=> b	Spaceship	a.compareTo(b)	java.lang.Comparable

 

class Money {

  private int    amount

  private String currency

  Money (amountValue, currencyValue) {

    amount   = amountValue

    currency = currencyValue

  }

 

  boolean equals (Object other) {

    if (null == other)              return false

    if (! (other instanceof Money)) return false

    if (currency != other.currency) return false

    if (amount    != other.amount)  return false

    return true

  }

 

  int hashCode() {

    amount.hashCode() + currency.hashCode()

  }

 

  Money plus (Money other) {

    if (null == other)    return null

    if (other.currency != currency) {

      throw new IllegalArgumentException("cannot add $other.currency to $currency")

    }

    return new Money(amount + other.amount, currency)

  }

}

def buck = new Money(1, 'USD')

d Use overridden ==

assert buck

assert buck == new Money(1, 'USD')

e Use overridden +

assert buck + buck == new Money(2, 'USD')