リストにハッシュをつけてランダムアクセスするデモ

RandomAccessTest.groovy

String getSHA1(String source) {
    java.security.MessageDigest md = java.security.MessageDigest.getInstance('SHA-1')
    md.update(source.getBytes('UTF-8'))
    md.digest().collect{ String.format('%02x', it) }.join()
}

def list = (1..10).collect{
    [it, getSHA1(it.toString())]
}
println list
println collect(list, 3)

def collect(list, num) {
    def hash = getSHA1(Runtime.runtime.freeMemory().toString())
    def result = []
    result.addAll list.findAll{ it[1] <= hash }
    if (result.size() >= num) {
        return result[0..<num]
    }
    result.addAll list.findAll{ it[1] > hash }
    println "2: ${result.size()}個"
    if (result.size() >= num) {
        return result[0..<num]
    }
    return result
}