Add timestamp field and methods to Chunk

Author: Glavo

src/main/java/org/glavo/nbt/chunk/Chunk.java

@@ -24,6 +24,9 @@
 import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.Nullable;
 
+import java.time.Instant;
+import java.util.Objects;
+
 /// Represents a chunk in a region file.
 ///
 ///  A chunk can contain a root tag, which is usually a compound tag containing the chunk data.
@@ -32,16 +35,34 @@ public final class Chunk implements NBTParent<CompoundTag>, NBTElement {
     int localIndex;
 
     @Nullable CompoundTag rootTag;
+    Instant timestamp = Instant.EPOCH;
 
     /// Creates a new empty chunk.
+    ///
+    /// The root tag is initially `null`, and the timestamp is set to the epoch (1970-01-01T00:00:00Z).
     public Chunk() {
     }
 
+    /// Creates a new empty chunk with the given timestamp.
+    ///
+    /// The root tag is initially `null`.
+    public Chunk(Instant timestamp) {
+        this.timestamp = Objects.requireNonNull(timestamp, "timestamp");
+    }
+
     /// Creates a new chunk with the given root tag.
+    ///
+    /// The timestamp is set to the epoch (1970-01-01T00:00:00Z).
     public Chunk(@Nullable CompoundTag rootTag) {
         setRootTag(rootTag);
     }
 
+    /// Creates a new chunk with the given timestamp and root tag.
+    public Chunk(Instant timestamp, @Nullable CompoundTag rootTag) {
+        this.timestamp = Objects.requireNonNull(timestamp, "timestamp");
+        setRootTag(rootTag);
+    }
+
     /// Return the region of this chunk, or `null` if this chunk is not in any region.
     @Contract(pure = true)
     public @Nullable ChunkRegion getRegion() {
@@ -109,6 +130,20 @@ public void setRootTag(@Nullable CompoundTag rootTag) {
         this.rootTag = rootTag;
     }
 
+    /// Return the timestamp of this chunk.
+    ///
+    /// The default value is the epoch (1970-01-01T00:00:00Z).
+    @Contract(pure = true)
+    public Instant getTimestamp() {
+        return timestamp;
+    }
+
+    /// Set the timestamp of this chunk.
+    @Contract(mutates = "this")
+    public void setTimestamp(Instant timestamp) {
+        this.timestamp = Objects.requireNonNull(timestamp, "timestamp");
+    }
+
     @Override
     @Contract(mutates = "this,param1")
     public void remove(CompoundTag element) throws IllegalArgumentException {