[main] Allow null in lazy supplier

src/main/java/io/gitlab/jfronny/commons/LazySupplier.java

@@ -2,6 +2,7 @@ package io.gitlab.jfronny.commons;
 
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.Objects;
 import java.util.function.Function;
@@ -13,16 +14,18 @@ import java.util.function.Supplier;
 public class LazySupplier<T> implements Supplier<T> {
     private final Supplier<T> supplier;
     private T cache = null;
+    private boolean initialized;
 
     /**
      * Create a lazy supplier from a pre-initialized value.
      * The backing supplier will be empty and never called.
      * @param value The value to initialize the cache with
      */
-    public LazySupplier(@NotNull T value) {
+    public LazySupplier(@Nullable T value) {
         this.supplier = () -> {
             throw new RuntimeException("Supplier should have never been called");
         };
+        initialized = true;
         cache = value;
     }
 
@@ -33,10 +36,11 @@ public class LazySupplier<T> implements Supplier<T> {
      */
     public LazySupplier(@NotNull Supplier<T> supplier) {
         this.supplier = Objects.requireNonNull(supplier);
+        initialized = false;
     }
 
     @Override @Contract(pure = true) @NotNull public T get() {
-        if (cache == null) cache = supplier.get();
+        if (!initialized) cache = supplier.get();
         return cache;
     }