From e81f3d715cb7d6f52f4406ad87981cece7f942d8 Mon Sep 17 00:00:00 2001
From: Johnny Lim <izeye@naver.com>
Date: Mon, 11 Dec 2023 00:08:17 +0900
Subject: [PATCH] Use cache for base time unit strings

Closes gh-4352
---
 .../java/io/micrometer/core/instrument/MeterRegistry.java   | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/micrometer-core/src/main/java/io/micrometer/core/instrument/MeterRegistry.java b/micrometer-core/src/main/java/io/micrometer/core/instrument/MeterRegistry.java
index d016131cca..0bb5e289b7 100644
--- a/micrometer-core/src/main/java/io/micrometer/core/instrument/MeterRegistry.java
+++ b/micrometer-core/src/main/java/io/micrometer/core/instrument/MeterRegistry.java
@@ -279,8 +279,12 @@ protected String getConventionName(Meter.Id id) {
      */
     protected abstract DistributionStatisticConfig defaultHistogramConfig();
 
+    private final EnumMap<TimeUnit, String> baseTimeUnitStringCache = new EnumMap<>(TimeUnit.class);
+
     private String getBaseTimeUnitStr() {
-        return getBaseTimeUnit().toString().toLowerCase();
+        TimeUnit baseTimeUnit = getBaseTimeUnit();
+        return this.baseTimeUnitStringCache.computeIfAbsent(baseTimeUnit,
+                (timeUnit) -> timeUnit.toString().toLowerCase());
     }
 
     /**