Create dedicated empty impls of segment/string-data

Author: Col-E

src/main/java/software/coley/lljzip/util/data/MemorySegmentData.java

@@ -25,7 +25,7 @@ default MemorySegmentData copy() {
 
 	@Nonnull
 	static MemorySegmentData empty() {
-		return FullSegment.EMPTY;
+		return EmptySegment.INSTANCE;
 	}
 
 	@Nonnull
@@ -85,7 +85,6 @@ public MemorySegment get() {
 	}
 
 	class FullSegment implements MemorySegmentData {
-		private static final FullSegment EMPTY = new FullSegment(MemorySegmentUtil.EMPTY);
 		private final MemorySegment segment;
 
 		public FullSegment(@Nonnull MemorySegment segment) {
@@ -104,4 +103,16 @@ public MemorySegmentData copy() {
 			return this;
 		}
 	}
+
+	class EmptySegment implements MemorySegmentData {
+		private static final EmptySegment INSTANCE = new EmptySegment();
+
+		private EmptySegment() {}
+
+		@Nonnull
+		@Override
+		public MemorySegment get() {
+			return MemorySegmentUtil.EMPTY;
+		}
+	}
 }

src/main/java/software/coley/lljzip/util/data/StringData.java

@@ -26,7 +26,7 @@ default StringData copy() {
 
 	@Nonnull
 	static StringData empty() {
-		return Literal.EMPTY;
+		return Empty.INSTANCE;
 	}
 
 	@Nonnull
@@ -101,7 +101,6 @@ public String get() {
 	}
 
 	class Literal implements StringData {
-		private static final Literal EMPTY = new Literal("");
 		private final String content;
 
 		public Literal(@Nonnull String content) {
@@ -120,4 +119,16 @@ public StringData copy() {
 			return this;
 		}
 	}
+
+	class Empty implements StringData {
+		private static final Empty INSTANCE = new Empty();
+
+		private Empty() {}
+
+		@Nonnull
+		@Override
+		public String get() {
+			return "";
+		}
+	}
 }