diff --git a/java/src/main/java/io/nayuki/qrcodegen/DataTooLongException.java b/java/src/main/java/io/nayuki/qrcodegen/DataTooLongException.java
index 0cbefc7..f1453ef 100644
--- a/java/src/main/java/io/nayuki/qrcodegen/DataTooLongException.java
+++ b/java/src/main/java/io/nayuki/qrcodegen/DataTooLongException.java
@@ -33,17 +33,17 @@ package io.nayuki.qrcodegen;
  *     if it was less than {@link QrCode#MAX_VERSION}. (This advice does not apply to the other
  *     factory functions because they search all versions up to {@code QrCode.MAX_VERSION}.)</p></li>
  *   <li><p>Split the text data into better or optimal segments in order to reduce the number of
- *     bits required. (See {@link QrSegmentAdvanced#makeSegmentsOptimally(String,QrCode.Ecc,int,int)
+ *     bits required. (See {@link QrSegmentAdvanced#makeSegmentsOptimally(CharSequence,QrCode.Ecc,int,int)
  *     QrSegmentAdvanced.makeSegmentsOptimally()}.)</p></li>
  *   <li><p>Change the text or binary data to be shorter.</p></li>
  *   <li><p>Change the text to fit the character set of a particular segment mode (e.g. alphanumeric).</p></li>
  *   <li><p>Propagate the error upward to the caller/user.</p></li>
  * </ul>
- * @see QrCode#encodeText(String, QrCode.Ecc)
+ * @see QrCode#encodeText(CharSequence, QrCode.Ecc)
  * @see QrCode#encodeBinary(byte[], QrCode.Ecc)
  * @see QrCode#encodeSegments(java.util.List, QrCode.Ecc)
  * @see QrCode#encodeSegments(java.util.List, QrCode.Ecc, int, int, int, boolean)
- * @see QrSegmentAdvanced#makeSegmentsOptimally(String, QrCode.Ecc, int, int)
+ * @see QrSegmentAdvanced#makeSegmentsOptimally(CharSequence, QrCode.Ecc, int, int)
  */
 public class DataTooLongException extends IllegalArgumentException {
 	
diff --git a/java/src/main/java/io/nayuki/qrcodegen/QrCode.java b/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
index 8e6ef09..ee7d28e 100644
--- a/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
+++ b/java/src/main/java/io/nayuki/qrcodegen/QrCode.java
@@ -37,7 +37,7 @@ import java.util.Objects;
  * from 1 to 40, all 4 error correction levels, and 4 character encoding modes.</p>
  * <p>Ways to create a QR Code object:</p>
  * <ul>
- *   <li><p>High level: Take the payload data and call {@link QrCode#encodeText(String,Ecc)}
+ *   <li><p>High level: Take the payload data and call {@link QrCode#encodeText(CharSequence,Ecc)}
  *     or {@link QrCode#encodeBinary(byte[],Ecc)}.</p></li>
  *   <li><p>Mid level: Custom-make the list of {@link QrSegment segments}
  *     and call {@link QrCode#encodeSegments(List,Ecc)} or
@@ -66,7 +66,7 @@ public final class QrCode {
 	 * @throws DataTooLongException if the text fails to fit in the
 	 * largest version QR Code at the ECL, which means it is too long
 	 */
-	public static QrCode encodeText(String text, Ecc ecl) {
+	public static QrCode encodeText(CharSequence text, Ecc ecl) {
 		Objects.requireNonNull(text);
 		Objects.requireNonNull(ecl);
 		List<QrSegment> segs = QrSegment.makeSegments(text);
@@ -102,7 +102,7 @@ public final class QrCode {
 	 * of the result may be higher than the ecl argument if it can be done without increasing the version.
 	 * <p>This function allows the user to create a custom sequence of segments that switches
 	 * between modes (such as alphanumeric and byte) to encode text in less space.
-	 * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)}
+	 * This is a mid-level API; the high-level API is {@link #encodeText(CharSequence,Ecc)}
 	 * and {@link #encodeBinary(byte[],Ecc)}.</p>
 	 * @param segs the segments to encode
 	 * @param ecl the error correction level to use (not {@code null}) (boostable)
@@ -125,7 +125,7 @@ public final class QrCode {
 	 * mask, or &#x2212;1 to automatically choose an appropriate mask (which may be slow).
 	 * <p>This function allows the user to create a custom sequence of segments that switches
 	 * between modes (such as alphanumeric and byte) to encode text in less space.
-	 * This is a mid-level API; the high-level API is {@link #encodeText(String,Ecc)}
+	 * This is a mid-level API; the high-level API is {@link #encodeText(CharSequence,Ecc)}
 	 * and {@link #encodeBinary(byte[],Ecc)}.</p>
 	 * @param segs the segments to encode
 	 * @param ecl the error correction level to use (not {@code null}) (boostable)
diff --git a/java/src/main/java/io/nayuki/qrcodegen/QrSegment.java b/java/src/main/java/io/nayuki/qrcodegen/QrSegment.java
index 73ccbfa..4e7118f 100644
--- a/java/src/main/java/io/nayuki/qrcodegen/QrSegment.java
+++ b/java/src/main/java/io/nayuki/qrcodegen/QrSegment.java
@@ -34,7 +34,7 @@ import java.util.regex.Pattern;
  * A segment of character/binary/control data in a QR Code symbol.
  * Instances of this class are immutable.
  * <p>The mid-level way to create a segment is to take the payload data and call a
- * static factory function such as {@link QrSegment#makeNumeric(String)}. The low-level
+ * static factory function such as {@link QrSegment#makeNumeric(CharSequence)}. The low-level
  * way to create a segment is to custom-make the bit buffer and call the {@link
  * QrSegment#QrSegment(Mode,int,BitBuffer) constructor} with appropriate values.</p>
  * <p>This segment class imposes no length restrictions, but QR Codes have restrictions.
@@ -72,7 +72,7 @@ public final class QrSegment {
 	 * @throws NullPointerException if the string is {@code null}
 	 * @throws IllegalArgumentException if the string contains non-digit characters
 	 */
-	public static QrSegment makeNumeric(String digits) {
+	public static QrSegment makeNumeric(CharSequence digits) {
 		Objects.requireNonNull(digits);
 		if (!isNumeric(digits))
 			throw new IllegalArgumentException("String contains non-numeric characters");
@@ -80,7 +80,7 @@ public final class QrSegment {
 		BitBuffer bb = new BitBuffer();
 		for (int i = 0; i < digits.length(); ) {  // Consume up to 3 digits per iteration
 			int n = Math.min(digits.length() - i, 3);
-			bb.appendBits(Integer.parseInt(digits.substring(i, i + n)), n * 3 + 1);
+			bb.appendBits(Integer.parseInt(digits.subSequence(i, i + n).toString()), n * 3 + 1);
 			i += n;
 		}
 		return new QrSegment(Mode.NUMERIC, digits.length(), bb);
@@ -96,7 +96,7 @@ public final class QrSegment {
 	 * @throws NullPointerException if the string is {@code null}
 	 * @throws IllegalArgumentException if the string contains non-encodable characters
 	 */
-	public static QrSegment makeAlphanumeric(String text) {
+	public static QrSegment makeAlphanumeric(CharSequence text) {
 		Objects.requireNonNull(text);
 		if (!isAlphanumeric(text))
 			throw new IllegalArgumentException("String contains unencodable characters in alphanumeric mode");
@@ -121,7 +121,7 @@ public final class QrSegment {
 	 * @return a new mutable list (not {@code null}) of segments (not {@code null}) containing the text
 	 * @throws NullPointerException if the text is {@code null}
 	 */
-	public static List<QrSegment> makeSegments(String text) {
+	public static List<QrSegment> makeSegments(CharSequence text) {
 		Objects.requireNonNull(text);
 		
 		// Select the most efficient segment encoding automatically
@@ -132,7 +132,7 @@ public final class QrSegment {
 		else if (isAlphanumeric(text))
 			result.add(makeAlphanumeric(text));
 		else
-			result.add(makeBytes(text.getBytes(StandardCharsets.UTF_8)));
+			result.add(makeBytes(text.toString().getBytes(StandardCharsets.UTF_8)));
 		return result;
 	}
 	
@@ -168,9 +168,9 @@ public final class QrSegment {
 	 * @param text the string to test for encodability (not {@code null})
 	 * @return {@code true} iff each character is in the range 0 to 9.
 	 * @throws NullPointerException if the string is {@code null}
-	 * @see #makeNumeric(String)
+	 * @see #makeNumeric(CharSequence)
 	 */
-	public static boolean isNumeric(String text) {
+	public static boolean isNumeric(CharSequence text) {
 		return NUMERIC_REGEX.matcher(text).matches();
 	}
 	
@@ -182,9 +182,9 @@ public final class QrSegment {
 	 * @param text the string to test for encodability (not {@code null})
 	 * @return {@code true} iff each character is in the alphanumeric mode character set
 	 * @throws NullPointerException if the string is {@code null}
-	 * @see #makeAlphanumeric(String)
+	 * @see #makeAlphanumeric(CharSequence)
 	 */
-	public static boolean isAlphanumeric(String text) {
+	public static boolean isAlphanumeric(CharSequence text) {
 		return ALPHANUMERIC_REGEX.matcher(text).matches();
 	}
 	
diff --git a/java/src/main/java/io/nayuki/qrcodegen/QrSegmentAdvanced.java b/java/src/main/java/io/nayuki/qrcodegen/QrSegmentAdvanced.java
index 8b60cc4..d018a65 100644
--- a/java/src/main/java/io/nayuki/qrcodegen/QrSegmentAdvanced.java
+++ b/java/src/main/java/io/nayuki/qrcodegen/QrSegmentAdvanced.java
@@ -48,7 +48,7 @@ public final class QrSegmentAdvanced {
 	 * in the specified {error correction level, minimum version number, maximum version number}.
 	 * <p>This function can utilize all four text encoding modes: numeric, alphanumeric, byte (UTF-8),
 	 * and kanji. This can be considered as a sophisticated but slower replacement for {@link
-	 * QrSegment#makeSegments(String)}. This requires more input parameters because it searches a
+	 * QrSegment#makeSegments(CharSequence)}. This requires more input parameters because it searches a
 	 * range of versions, like {@link QrCode#encodeSegments(List,QrCode.Ecc,int,int,int,boolean)}.</p>
 	 * @param text the text to be encoded (not {@code null}), which can be any Unicode string
 	 * @param ecl the error correction level to use (not {@code null})
@@ -60,7 +60,7 @@ public final class QrSegmentAdvanced {
 	 * @throws IllegalArgumentException if 1 &#x2264; minVersion &#x2264; maxVersion &#x2264; 40 is violated
 	 * @throws DataTooLongException if the text fails to fit in the maxVersion QR Code at the ECL
 	 */
-	public static List<QrSegment> makeSegmentsOptimally(String text, QrCode.Ecc ecl, int minVersion, int maxVersion) {
+	public static List<QrSegment> makeSegmentsOptimally(CharSequence text, QrCode.Ecc ecl, int minVersion, int maxVersion) {
 		// Check arguments
 		Objects.requireNonNull(text);
 		Objects.requireNonNull(ecl);
@@ -223,7 +223,7 @@ public final class QrSegmentAdvanced {
 	
 	// Returns a new array of Unicode code points (effectively
 	// UTF-32 / UCS-4) representing the given UTF-16 string.
-	private static int[] toCodePoints(String s) {
+	private static int[] toCodePoints(CharSequence s) {
 		int[] result = s.codePoints().toArray();
 		for (int c : result) {
 			if (Character.isSurrogate((char)c))
@@ -257,9 +257,9 @@ public final class QrSegmentAdvanced {
 	 * @return a segment (not {@code null}) containing the text
 	 * @throws NullPointerException if the string is {@code null}
 	 * @throws IllegalArgumentException if the string contains non-encodable characters
-	 * @see #isEncodableAsKanji(String)
+	 * @see #isEncodableAsKanji(CharSequence)
 	 */
-	public static QrSegment makeKanji(String text) {
+	public static QrSegment makeKanji(CharSequence text) {
 		Objects.requireNonNull(text);
 		BitBuffer bb = new BitBuffer();
 		text.chars().forEachOrdered(c -> {
@@ -281,9 +281,9 @@ public final class QrSegmentAdvanced {
 	 * @param text the string to test for encodability (not {@code null})
 	 * @return {@code true} iff each character is in the kanji mode character set
 	 * @throws NullPointerException if the string is {@code null}
-	 * @see #makeKanji(String)
+	 * @see #makeKanji(CharSequence)
 	 */
-	public static boolean isEncodableAsKanji(String text) {
+	public static boolean isEncodableAsKanji(CharSequence text) {
 		Objects.requireNonNull(text);
 		return text.chars().allMatch(
 			c -> isKanji((char)c));