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September 19, 2009

Groovy Goodness: Working with Arrays

Groovy supports arrays just like in Java. We only get a lot more methods because of the GDK extensions added to arrays. The only we thing we need to consider is the way we initialize arrays. In Java we can define and populate an array with the following code: String[] s = new String[] { "a", "b" };, but in Groovy we cannot use this syntax. In Groovy the previous statement would become String[] s = ["a", "b"] as String[].

def strArray = new String[3]
assert strArray instanceof String[]
strArray[0] = 'mrhaki'
strArray.putAt(1, 'Groovy')  // New syntax.
strArray[2] = 'Java'

assert 'mrhaki' == strArray.getAt(0)  // Just another way to get a value.
assert 'Groovy' == strArray[1]
assert 'Java' == strArray[-1]  // Negative indeces allowed.
assert ['mrhaki', 'Groovy'] == strArray[0..1]  // We can use ranges.
assert ['mrhaki', 'Java'] == strArray[0, 2]

assert 3 == strArray.length  // Normal length property for arrays.
assert 3 == strArray.size()  // Groovy adds size() method as well.

// We can use min() and max() methods.
assert 42 == [102,301,42,83].min()
assert 301 == [102,301,42,83].max()
assert 'Java' == strArray.min { it.size() }
assert 'mrhaki' == strArray.max { it[0] as char }

// We can even use the Collection GDK methods on an array.
strArray.eachWithIndex { value, idx -> assert value == strArray[idx] }
assert ['ikahrm', 'yvoorG', 'avaJ'] == strArray.collect { it.reverse() }
assert 'Groovy' == strArray.find { it =~ /Groovy/ }

// We can remove values with the '-' operator.
assert ['Groovy', 'Java'] == strArray - 'mrhaki'

// Other useful methods for arrays.
assert ['Java', 'Groovy', 'mrhaki'] == strArray.reverse()
assert ['Groovy', 'Java', 'mrhaki'] == strArray.sort()
assert 1 == strArray.count('mrhaki')

// Convert to ArrayList.
def strList = strArray.toList()
assert 'java.util.ArrayList' == strList.class.name

// Convert ArrayList to array object.
def otherArray = strList as String[]
assert otherArray instanceof String[]