refactor: add VarBinArray.getString() and use it everywhere

Replace all `new String(va.getBytes(i), StandardCharsets.UTF_8)` call
sites with the new convenience method. Remove now-unused imports.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

cli/src/main/java/io/github/dfa1/vortex/cli/FilterCommand.java

@@ -142,7 +142,7 @@ private static int compareValue(Array arr, long rowIdx, Comparable<?> value) {
             case FloatArray fa  -> compareDouble(fa.getFloat(rowIdx), value);
             case BoolArray ba  -> Boolean.compare(ba.getBoolean(rowIdx), (Boolean) value);
             case VarBinArray va -> {
-                String v = new String(va.getBytes(rowIdx), StandardCharsets.UTF_8);
+                String v = va.getString(rowIdx);
                 yield v.compareTo((String) value);
             }
             default -> throw new IllegalArgumentException(

core/src/main/java/io/github/dfa1/vortex/core/array/VarBinArray.java

@@ -8,6 +8,7 @@
 
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.ValueLayout;
+import java.nio.charset.StandardCharsets;
 import java.util.function.IntConsumer;
 
 /// Concrete [Array] for variable-length binary / UTF-8 string columns.
@@ -130,6 +131,10 @@ public byte[] getBytes(long i) {
 		return out;
 	}
 
+	public String getString(long i) {
+		return new String(getBytes(i), StandardCharsets.UTF_8);
+	}
+
 	public int getByteLength(long i) {
 		if (dictCodesSegs != null) {
 			long code = dictReadCode(i);

core/src/test/java/io/github/dfa1/vortex/core/array/VarBinArrayTest.java

@@ -47,8 +47,8 @@ void getBytes_returnsCorrectBytes() {
 			VarBinArray sut = of("hello", "world");
 
 			// When / Then
-			assertThat(new String(sut.getBytes(0), StandardCharsets.UTF_8)).isEqualTo("hello");
-			assertThat(new String(sut.getBytes(1), StandardCharsets.UTF_8)).isEqualTo("world");
+			assertThat(sut.getString(0)).isEqualTo("hello");
+			assertThat(sut.getString(1)).isEqualTo("world");
 		}
 
 		@Test
@@ -125,9 +125,9 @@ void getBytes_resolvesViaDict() {
 			VarBinArray sut = ofDict(new String[]{"foo", "bar"}, new int[]{1, 0, 1});
 
 			// When / Then
-			assertThat(new String(sut.getBytes(0), StandardCharsets.UTF_8)).isEqualTo("bar");
-			assertThat(new String(sut.getBytes(1), StandardCharsets.UTF_8)).isEqualTo("foo");
-			assertThat(new String(sut.getBytes(2), StandardCharsets.UTF_8)).isEqualTo("bar");
+			assertThat(sut.getString(0)).isEqualTo("bar");
+			assertThat(sut.getString(1)).isEqualTo("foo");
+			assertThat(sut.getString(2)).isEqualTo("bar");
 		}
 
 		@Test

core/src/test/java/io/github/dfa1/vortex/encoding/DictEncodingTest.java

@@ -13,7 +13,6 @@
 import java.lang.foreign.MemorySegment;
 import java.lang.foreign.ValueLayout;
 import java.nio.ByteOrder;
-import java.nio.charset.StandardCharsets;
 import java.util.stream.Stream;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -107,7 +106,7 @@ void encodeDecode_utf8_isLossless(String name, String[] data) {
 			VarBinArray arr = (VarBinArray) result;
 			assertThat(arr.length()).isEqualTo(data.length);
 			for (int i = 0; i < data.length; i++) {
-				String actual = new String(arr.getBytes(i), StandardCharsets.UTF_8);
+				String actual = arr.getString(i);
 				assertThat(actual).as("index %d", i).isEqualTo(data[i]);
 			}
 		}

core/src/test/java/io/github/dfa1/vortex/encoding/SparseEncodingTest.java

@@ -308,9 +308,9 @@ void decode_utf8_withPatches_writesStringsAtIndices() {
 			VarBinArray varBin = (VarBinArray) result;
 			assertThat(varBin.length()).isEqualTo(5L);
 			assertThat(varBin.getByteLength(0)).isZero();
-			assertThat(new String(varBin.getBytes(1))).isEqualTo("hi");
+			assertThat(varBin.getString(1)).isEqualTo("hi");
 			assertThat(varBin.getByteLength(2)).isZero();
-			assertThat(new String(varBin.getBytes(3))).isEqualTo("bye");
+			assertThat(varBin.getString(3)).isEqualTo("bye");
 			assertThat(varBin.getByteLength(4)).isZero();
 		}
 

core/src/test/java/io/github/dfa1/vortex/encoding/VarBinViewEncodingTest.java

@@ -91,7 +91,7 @@ void decode_roundtrip_returnsAllStrings(String name, String[] values) {
 			assertThat(result.length()).isEqualTo(n);
 			for (int i = 0; i < values.length; i++) {
 				VarBinArray varBinArray = (VarBinArray) result;
-				String decoded = new String(varBinArray.getBytes(i), StandardCharsets.UTF_8);
+				String decoded = varBinArray.getString(i);
 				assertThat(decoded).as("index %d", i).isEqualTo(values[i]);
 			}
 		}

csv/src/main/java/io/github/dfa1/vortex/csv/CsvExporter.java

@@ -20,7 +20,6 @@
 import java.io.FilterWriter;
 import java.io.IOException;
 import java.io.Writer;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.List;
 
@@ -112,7 +111,7 @@ private static String cellValue(Array arr, long rowIdx) {
             case DoubleArray da -> Double.toString(da.getDouble(rowIdx));
             case FloatArray fa -> Float.toString(fa.getFloat(rowIdx));
             case BoolArray ba -> Boolean.toString(ba.getBoolean(rowIdx));
-            case VarBinArray va -> new String(va.getBytes(rowIdx), StandardCharsets.UTF_8);
+            case VarBinArray va -> va.getString(rowIdx);
             default -> throw new VortexException(
                     "unsupported array type for CSV export: " + arr.getClass().getSimpleName());
         };

csv/src/test/java/io/github/dfa1/vortex/csv/CsvImporterTest.java

@@ -12,7 +12,6 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.io.TempDir;
 
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 
@@ -48,8 +47,8 @@ void infersTypedColumnsAndRoundTrips(@TempDir Path tmp) throws Exception {
                 assertThat(ids.getLong(0)).isEqualTo(1L);
                 assertThat(ids.getLong(1)).isEqualTo(2L);
                 VarBinArray names = chunk.column("name");
-                assertThat(new String(names.getBytes(0), StandardCharsets.UTF_8)).isEqualTo("Alice");
-                assertThat(new String(names.getBytes(1), StandardCharsets.UTF_8)).isEqualTo("Bob");
+                assertThat(names.getString(0)).isEqualTo("Alice");
+                assertThat(names.getString(1)).isEqualTo("Bob");
             }
         }
     }
@@ -110,7 +109,7 @@ void respectsSchemaOverride(@TempDir Path tmp) throws Exception {
                 assertThat(iter.hasNext()).isTrue();
                 ScanResult chunk = iter.next();
                 VarBinArray values = chunk.column("value");
-                assertThat(new String(values.getBytes(0), StandardCharsets.UTF_8)).isEqualTo("42");
+                assertThat(values.getString(0)).isEqualTo("42");
             }
         }
     }