package net.dimensions;

import java.util.Random;

public class Dimensions {

    private static Random rand;

    public static void init() {
        System.out.println("Initializing Dimensions...");
        rand = new Random();
    }

    public static Random getRandom(){
        return rand;
    }
}

package net.dimensions;

public class Dimensions
{
    public static void init()
    {
        System.out.println("Initializing Dimensions...");
    }
}
--- 
+++ 
@@ -1,9 +1,17 @@
 package net.dimensions;
 
-public class Dimensions
-{
-    public static void init()
-    {
+import java.util.Random;
+
+public class Dimensions {
+
+    private static Random rand;
+
+    public static void init() {
         System.out.println("Initializing Dimensions...");
+        rand = new Random();
+    }
+
+    public static Random getRandom(){
+        return rand;
     }
 }
Add Random instance into main class

So each plugin that uses a Random doesn't have to create it's own instance, but they are free to if they want to make one with a custom seed.