From 342216bb71a118107034ea774af24d46487a99d0 Mon Sep 17 00:00:00 2001
From: iamdanfox <iamdanfox@gmail.com>
Date: Tue, 22 Jun 2021 15:27:33 +0100
Subject: [PATCH] [break] Stop using Matcher.group() which allocates a string
 (#466)

Parsing all types of sls version no longer involves allocating strings just to parse them as integers again.
---
 build.gradle                                        |  2 +-
 changelog/@unreleased/pr-466.v2.yml                 |  6 ++++++
 .../java/com/palantir/sls/versions/MatchResult.java | 13 +++++++++++--
 .../java/com/palantir/sls/versions/RegexParser.java |  2 +-
 4 files changed, 19 insertions(+), 4 deletions(-)
 create mode 100644 changelog/@unreleased/pr-466.v2.yml

diff --git a/build.gradle b/build.gradle
index c1bda35a..3e316249 100644
--- a/build.gradle
+++ b/build.gradle
@@ -44,7 +44,7 @@ subprojects {
     apply plugin: 'org.inferred.processors'
 
     tasks.check.dependsOn(javadoc)
-    sourceCompatibility = 1.8
+    sourceCompatibility = 11
 
     tasks.withType(JavaCompile) {
         options.compilerArgs += ['-Werror']
diff --git a/changelog/@unreleased/pr-466.v2.yml b/changelog/@unreleased/pr-466.v2.yml
new file mode 100644
index 00000000..47d7719a
--- /dev/null
+++ b/changelog/@unreleased/pr-466.v2.yml
@@ -0,0 +1,6 @@
+type: break
+break:
+  description: This library now requires Java 11+ (previously it could run on Java
+    8+). This allows us to eliminate some String allocations from parsing SLS versions.
+  links:
+  - https://github.com/palantir/sls-version-java/pull/466
diff --git a/sls-versions/src/main/java/com/palantir/sls/versions/MatchResult.java b/sls-versions/src/main/java/com/palantir/sls/versions/MatchResult.java
index 66e2afe7..6ab0cc06 100644
--- a/sls-versions/src/main/java/com/palantir/sls/versions/MatchResult.java
+++ b/sls-versions/src/main/java/com/palantir/sls/versions/MatchResult.java
@@ -26,15 +26,24 @@ interface MatchResult {
     int groupCount();
 
     final class RegexMatchResult implements MatchResult {
+        private static final int RADIX = 10;
+        private final String string;
         private final Matcher matcher;
 
-        RegexMatchResult(Matcher matcher) {
+        RegexMatchResult(String string, Matcher matcher) {
+            this.string = string;
             this.matcher = matcher;
         }
 
         @Override
         public int groupAsInt(int group) {
-            return Integer.parseInt(matcher.group(group));
+            int groupStart = matcher.start(group);
+            int groupEnd = matcher.end(group);
+            if (groupStart == -1) {
+                throw new NumberFormatException();
+            }
+
+            return Integer.parseUnsignedInt(string, groupStart, groupEnd, RADIX);
         }
 
         @Override
diff --git a/sls-versions/src/main/java/com/palantir/sls/versions/RegexParser.java b/sls-versions/src/main/java/com/palantir/sls/versions/RegexParser.java
index e9df1324..d1912a3c 100644
--- a/sls-versions/src/main/java/com/palantir/sls/versions/RegexParser.java
+++ b/sls-versions/src/main/java/com/palantir/sls/versions/RegexParser.java
@@ -43,7 +43,7 @@ static RegexParser of(String regex) {
     @Nullable
     public MatchResult tryParse(String string) {
         Matcher matcher = pattern.matcher(string);
-        return matcher.matches() ? new MatchResult.RegexMatchResult(matcher) : null;
+        return matcher.matches() ? new MatchResult.RegexMatchResult(string, matcher) : null;
     }
 
     @Override