Debug.java

package simpledb;

/**
 * Debug is a utility class that wraps println statements and allows
 * more or less command line output to be turned on.
 * <p>
 * Change the value of the DEBUG_LEVEL constant using a system property:
 * simpledb.Debug. For example, on the command line, use -Dsimpledb.Debug=x,
 * or simply -Dsimpledb.Debug to enable it at level 0.
 * The log(level, message, ...) method will print to standard output if the
 * level number is less than or equal to the currently set DEBUG_LEVEL.
 */

public class Debug {
 private static final int DEBUG_LEVEL;
 static {
 String debug = System.getProperty("simpledb.Debug");
 if (debug == null) {
 // No system property = disabled
 DEBUG_LEVEL = -1;
 } else if (debug == "") {
 // Empty property = level 0
 DEBUG_LEVEL = 0;
 } else {
 DEBUG_LEVEL = Integer.parseInt(debug);
 }
 }

 private static final int DEFAULT_LEVEL = 0;

 /** Log message if the log level >= level. Uses printf. */
 public static void log(int level, String message, Object... args) {
 if (isEnabled(level)) {
 System.out.printf(message, args);
 System.out.println();
 }
 }

 /** @return true if level is being logged. */
 public static boolean isEnabled(int level) {
 return level <= DEBUG_LEVEL;
 }

 /** @return true if the default level is being logged. */
 public static boolean isEnabled() {
 return isEnabled(DEFAULT_LEVEL);
 }

 /** Logs message at the default log level. */
 public static void log(String message, Object... args) {
 log(DEFAULT_LEVEL, message, args);
 }
}