Minor optimization for tests

idea/tests/org/jetbrains/jet/plugin/MockLibraryUtil.java

@@ -1,6 +1,7 @@
 package org.jetbrains.jet.plugin;
 
 import com.intellij.util.io.ZipUtil;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.jet.JetTestUtils;
 import org.jetbrains.jet.cli.common.ExitCode;
 import org.jetbrains.jet.cli.jvm.K2JVMCompiler;
@@ -9,6 +10,7 @@ import org.jetbrains.jet.utils.PathUtil;
 
 import java.io.*;
 import java.lang.reflect.Method;
+import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLClassLoader;
 import java.util.zip.ZipOutputStream;
@@ -16,6 +18,9 @@ import java.util.zip.ZipOutputStream;
 import static junit.framework.Assert.assertEquals;
 
 public class MockLibraryUtil {
+
+    private static Class<?> compilerClass = null;
+
     public static File compileLibraryToJar(String sourcesPath) {
         try {
             File contentDir = JetTestUtils.tmpDir("lib-content");
@@ -37,15 +42,11 @@ public class MockLibraryUtil {
         }
     }
 
+    // Runs compiler in custom class loader to avoid effects caused by replacing Application with another one created in compiler.
     private static void compile(String sourcesPath, File outDir) {
         try {
             ByteArrayOutputStream outStream = new ByteArrayOutputStream();
-
-            // Running compiler in custom class loader to avoid effects caused by replacing Application with another one created in compiler.
-            File kotlinCompilerJar = new File(PathUtil.getKotlinPathsForDistDirectory().getLibPath(), "kotlin-compiler.jar");
-            URLClassLoader classLoader = new URLClassLoader(new URL[] {kotlinCompilerJar.toURI().toURL()}, Object.class.getClassLoader());
-
-            Class<?> compilerClass = classLoader.loadClass(K2JVMCompiler.class.getName());
+            Class<?> compilerClass = getCompilerClass();
             Object compilerObject = compilerClass.newInstance();
             Method execMethod = compilerClass.getMethod("exec", PrintStream.class, String[].class);
 
@@ -61,6 +62,18 @@ public class MockLibraryUtil {
         }
     }
 
+    @NotNull
+    private static Class<?> getCompilerClass() throws MalformedURLException, ClassNotFoundException {
+
+        if (compilerClass == null) {
+            File kotlinCompilerJar = new File(PathUtil.getKotlinPathsForDistDirectory().getLibPath(), "kotlin-compiler.jar");
+            URLClassLoader classLoader = new URLClassLoader(new URL[] {kotlinCompilerJar.toURI().toURL()}, Object.class.getClassLoader());
+
+            compilerClass = classLoader.loadClass(K2JVMCompiler.class.getName());
+        }
+        return compilerClass;
+    }
+
     private MockLibraryUtil() {
     }
 }