Polish variables

Extract a few more variables to make the format command easier to
follow.

Author: philwebb

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/logging/java/SimpleFormatter.java

@@ -42,11 +42,13 @@ public class SimpleFormatter extends Formatter {
 	public String format(LogRecord record) {
 		Date date = new Date(record.getMillis());
 		String source = record.getLoggerName();
+		String loggerName = record.getLoggerName();
+		String level = record.getLevel().getLocalizedName();
 		String message = formatMessage(record);
 		String throwable = getThrowable(record);
 		String thread = getThreadName();
-		return String.format(this.format, date, source, record.getLoggerName(), record.getLevel().getLocalizedName(),
-				message, throwable, thread, this.pid);
+		String pid = this.pid;
+		return String.format(this.format, date, source, loggerName, level, message, throwable, thread, pid);
 	}
 
 	private String getThrowable(LogRecord record) {