Revert "Convert Constants into an interface."

This reverts commit e7f2f43a715d8216f2d6fe78201e9e0adfacb606.

git-svn-id: https://svn.apache.org/repos/asf/logging/log4j/log4j2/trunk@1621040 13f79535-47bb-0310-9956-ffa450edef68

log4j-core/src/main/java/org/apache/logging/log4j/core/util/Constants.java

diff --git a/log4j-core/src/main/java/org/apache/logging/log4j/core/util/Constants.java b/log4j-core/src/main/java/org/apache/logging/log4j/core/util/Constants.java
index f5061be..20e47b6 100644
--- a/log4j-core/src/main/java/org/apache/logging/log4j/core/util/Constants.java
+++ b/log4j-core/src/main/java/org/apache/logging/log4j/core/util/Constants.java
@@ -21,32 +21,38 @@
 /**
  * Log4j Constants.
  */
-public interface Constants {
+public final class Constants {
 
     /**
      * Name of the system property to use to identify the LogEvent factory.
      */
-    String LOG4J_LOG_EVENT_FACTORY = "Log4jLogEventFactory";
+    public static final String LOG4J_LOG_EVENT_FACTORY = "Log4jLogEventFactory";
 
     /**
      * Name of the system property to use to identify the ContextSelector Class.
      */
-    String LOG4J_CONTEXT_SELECTOR = "Log4jContextSelector";
+    public static final String LOG4J_CONTEXT_SELECTOR = "Log4jContextSelector";
 
-    String LOG4J_DEFAULT_STATUS_LEVEL = "Log4jDefaultStatusLevel";
+    public static final String LOG4J_DEFAULT_STATUS_LEVEL = "Log4jDefaultStatusLevel";
 
     /**
      * JNDI context name string literal.
      */
-    String JNDI_CONTEXT_NAME = "java:comp/env/log4j/context-name";
+    public static final String JNDI_CONTEXT_NAME = "java:comp/env/log4j/context-name";
 
     /**
      * Line separator.
      */
-    String LINE_SEPARATOR = PropertiesUtil.getProperties().getStringProperty("line.separator", "\n");
+    public static final String LINE_SEPARATOR = PropertiesUtil.getProperties().getStringProperty("line.separator", "\n");
 
     /**
      * Number of milliseconds in a second.
      */
-    int MILLIS_IN_SECONDS = 1000;
+    public static final int MILLIS_IN_SECONDS = 1000;
+
+    /**
+     * Prevent class instantiation.
+     */
+    private Constants() {
+    }
 }