refactor(env/java): improve tests and implementation (#1246)

This basically fixes up the changes from #1220.

* test(env/java): replace test that duplicates implementation
* test(env/java): stub _ensure to focus on unit under test
* test(env/java): add test for invalid output
* refactor(env/java): keep try block small
* refactor(env/java): shorten excessive comment

bin/templates/cordova/lib/env/java.js

@@ -41,30 +41,9 @@ const java = {
         await java._ensure(process.env);
 
         // Java <= 8 writes version info to stderr, Java >= 9 to stdout
-        let version = null;
+        let javacOutput;
         try {
-            const javacOutput = (await execa('javac', ['-version'], { all: true })).all;
-
-            /*
-            A regex match for the java version looks like the following:
-
-            version: [
-                'javac 1.8.0',
-                '1.8.0',
-                index: 45,
-                input: 'Picked up _JAVA_OPTIONS: -Xms1024M -Xmx2048M\njavac 1.8.0_271',
-                groups: undefined
-            ]
-
-            We have to use a regular expression to get the java version, because on some environments
-            (e.g. macOS Big Sur) javac prints _JAVA_OPTIONS before printing the version and semver.coerce()
-            will fail to get the correct version from the output.
-            */
-
-            const match = /javac\s+([\d.]+)/i.exec(javacOutput);
-            if (match && match[1]) {
-                version = match[1];
-            }
+            javacOutput = (await execa('javac', ['-version'], { all: true })).all;
         } catch (ex) {
             events.emit('verbose', ex.shortMessage);
 
@@ -79,7 +58,11 @@ const java = {
             throw new CordovaError(msg);
         }
 
-        return semver.coerce(version);
+        // We have to filter the output, because javac prints _JAVA_OPTIONS
+        // before printing the version which causes semver.coerce to fail to get
+        // the correct version if those options contain any numbers.
+        const match = /javac\s+([\d.]+)/i.exec(javacOutput);
+        return semver.coerce(match && match[1]);
     },
 
     /**