Slight;y better logic to look for tools.jar

Favor JAVA_HOME env var over system prop.

Look both in java home and its parrent for "lib/tools.jar"

eclipse-language-servers/org.springframework.tooling.ls.eclipse.commons/src/org/springframework/tooling/ls/eclipse/commons/STS4LanguageServerProcessStreamConnector.java

@@ -12,8 +12,11 @@ package org.springframework.tooling.ls.eclipse.commons;
 
 import java.io.File;
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Consumer;
 
-import org.eclipse.core.runtime.Path;
 import org.eclipse.jdt.internal.launching.StandardVMType;
 import org.eclipse.lsp4e.server.ProcessStreamConnectionProvider;
 
@@ -50,11 +53,58 @@ public class STS4LanguageServerProcessStreamConnector extends ProcessStreamConne
 		return null;
 	}
 	
-	protected String getToolsJAR() {
-		File jre = new File(System.getProperty("java.home"));
-		return new File(jre.getParent(), "lib" + Path.SEPARATOR + "tools.jar").getAbsolutePath();
+	/**
+	 * Different places to look for tools jar, relative to Java home.
+	 */
+	private static String [] TOOLS_JAR_PATHS = {
+			"../lib/tools.jar",
+			"lib/tools.jar"
+	};
+	
+	protected File getToolsJAR() {
+		List<File> jhomes = new ArrayList<>(2);
+		resolve(System.getenv("JAVA_HOME"), jhomes::add);
+		resolve(System.getProperty("java.home"), jhomes::add);
+		for (File jhome : jhomes) {
+			for (String tjPath : TOOLS_JAR_PATHS) {
+				File toolsJar = new File(jhome, tjPath);
+				if (toolsJar.isFile()) {
+					return toolsJar;
+				}
+			}
+		}
+		return null;
 	}
 	
+	private void resolve(String path, Consumer<File> requestor) {
+		if (path!=null) {
+			try {
+				File file = new File(path).getCanonicalFile();
+				if (file.exists()) {
+					requestor.accept(file);
+					return;
+				}
+			} catch (IOException e) {
+				//Ignore... this can happen because it tries to handle symbolic links
+			}
+		}
+	}
+	
+	private File getJavaHomeFromEnv() {
+		try {
+			File jhome = new File(System.getenv("JAVA_HOME"));
+			if (jhome!=null) {
+				jhome = jhome.getCanonicalFile();
+				if (jhome.isDirectory()) {
+					return jhome;
+				}
+			}
+		} catch (IOException e) {
+			//Ignore... this can happen because it tries to handle symbolic links
+		}
+		return null;
+	}
+
 	protected String getWorkingDirLocation() {
 		return System.getProperty("user.dir");
 	}