tech.harmonysoft.oss.common.collection.CollectionInitializer.kt Maven / Gradle / Ivy

Go to download
package tech.harmonysoft.oss.common.collection

import java.util.*
import java.util.concurrent.ConcurrentHashMap

/**
 * Quite often many lambda objects are generated during frequent calls like [getOrPut]:
 *
 * ```
 * class MyClass {
 *     private val cache = mutableMapOf>()
 *
 *     fun service(key: String) {
 *         cache.getOrPut(key) { Stack() }
 *     }
 * }
 * ```
 *
 * That way it's more effective pre-defining initializers and use them like below - by doing that we avoie
 * unnecessary lambda objects construction:
 *
 * ```
 * cache.getOrPut(key, CollectionInitializer.stack())
 * ```
 */
@Suppress("UNCHECKED_CAST")
object CollectionInitializer {

    private val STACK: () -> Stack = { Stack() }
    private val MUTABLE_LIST: () -> MutableList = { mutableListOf() }
    private val MUTABLE_SET: () -> MutableSet = { mutableSetOf() }
    private val MUTABLE_MAP: () -> MutableMap = { mutableMapOf() }
    private val CONCURRENT_HASH_SET: () -> MutableSet = { Collections.newSetFromMap(ConcurrentHashMap()) }
    private val CONCURRENT_HASH_MAP: () -> ConcurrentHashMap = { ConcurrentHashMap() }

    fun  stack(): () -> Stack = STACK as () -> Stack
    fun  mutableList(): () -> MutableList = MUTABLE_LIST as () -> MutableList
    fun  mutableSet(): () -> MutableSet = MUTABLE_SET as () -> MutableSet
    fun  mutableMap(): () -> MutableMap = MUTABLE_MAP as () -> MutableMap
    fun  concurrentHashSet(): () -> MutableSet = CONCURRENT_HASH_SET as () -> MutableSet
    fun  concurrentHashMap(): () -> ConcurrentHashMap = CONCURRENT_HASH_MAP as () -> ConcurrentHashMap
}