DecimalFormats are not thread safe

app/src/main/java/com/vitorpamplona/amethyst/ui/note/ReactionsRow.kt

@@ -140,9 +140,6 @@ import kotlinx.collections.immutable.toImmutableMap
 import kotlinx.collections.immutable.toImmutableSet
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
-import java.math.BigDecimal
-import java.math.RoundingMode
-import java.text.DecimalFormat
 import kotlin.math.roundToInt
 
 @Composable
@@ -1519,31 +1516,3 @@ fun showCount(count: Int?): String {
         else -> "$count"
     }
 }
-
-val TenGiga = BigDecimal(10000000000)
-val OneGiga = BigDecimal(1000000000)
-val TenMega = BigDecimal(10000000)
-val OneMega = BigDecimal(1000000)
-val TenKilo = BigDecimal(10000)
-val OneKilo = BigDecimal(1000)
-
-var dfGBig: DecimalFormat = DecimalFormat("#.#G")
-var dfGSmall: DecimalFormat = DecimalFormat("#.0G")
-var dfMBig: DecimalFormat = DecimalFormat("#.#M")
-var dfMSmall: DecimalFormat = DecimalFormat("#.0M")
-var dfK: DecimalFormat = DecimalFormat("#.#k")
-var dfN: DecimalFormat = DecimalFormat("#")
-
-fun showAmount(amount: BigDecimal?): String {
-    if (amount == null) return ""
-    if (amount.abs() < BigDecimal(0.01)) return ""
-
-    return when {
-        amount >= TenGiga -> dfGBig.format(amount.div(OneGiga).setScale(0, RoundingMode.HALF_UP))
-        amount >= OneGiga -> dfGSmall.format(amount.div(OneGiga).setScale(0, RoundingMode.HALF_UP))
-        amount >= TenMega -> dfMBig.format(amount.div(OneMega).setScale(0, RoundingMode.HALF_UP))
-        amount >= OneMega -> dfMSmall.format(amount.div(OneMega).setScale(0, RoundingMode.HALF_UP))
-        amount >= TenKilo -> dfK.format(amount.div(OneKilo).setScale(0, RoundingMode.HALF_UP))
-        else -> dfN.format(amount)
-    }
-}

app/src/main/java/com/vitorpamplona/amethyst/ui/note/ZapFormatter.kt

@@ -0,0 +1,76 @@
+/**
+ * Copyright (c) 2024 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.note
+
+import java.math.BigDecimal
+import java.math.RoundingMode
+import java.text.DecimalFormat
+
+val TenGiga = BigDecimal(10000000000)
+val OneGiga = BigDecimal(1000000000)
+val TenMega = BigDecimal(10000000)
+val OneMega = BigDecimal(1000000)
+val TenKilo = BigDecimal(10000)
+val OneKilo = BigDecimal(1000)
+
+private val dfGBig =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#.#G")
+    }
+
+private val dfGSmall =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#.0G")
+    }
+
+private val dfMBig =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#.#M")
+    }
+
+private val dfMSmall =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#.0M")
+    }
+
+private val dfK =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#.#k")
+    }
+
+private val dfN =
+    object : ThreadLocal<DecimalFormat>() {
+        override fun initialValue() = DecimalFormat("#")
+    }
+
+fun showAmount(amount: BigDecimal?): String {
+    if (amount == null) return ""
+    if (amount.abs() < BigDecimal(0.01)) return ""
+
+    return when {
+        amount >= TenGiga -> dfGBig.get().format(amount.div(OneGiga).setScale(0, RoundingMode.HALF_UP))
+        amount >= OneGiga -> dfGSmall.get().format(amount.div(OneGiga).setScale(0, RoundingMode.HALF_UP))
+        amount >= TenMega -> dfMBig.get().format(amount.div(OneMega).setScale(0, RoundingMode.HALF_UP))
+        amount >= OneMega -> dfMSmall.get().format(amount.div(OneMega).setScale(0, RoundingMode.HALF_UP))
+        amount >= TenKilo -> dfK.get().format(amount.div(OneKilo).setScale(0, RoundingMode.HALF_UP))
+        else -> dfN.get().format(amount)
+    }
+}