Add unwrite() and getLastChar() to SimpleWriter which now extends Appendable

Author: carlosame

junit/io/sf/carte/util/BufferSimpleWriterTest.java

@@ -33,6 +33,10 @@ public void testBufferSimpleWriter() throws IOException {
 		assertEquals("abcdef1", wri.toString());
 		wri.unwrite(2);
 		assertEquals("abcde", wri.toString());
+		wri.append('g');
+		assertEquals("abcdeg", wri.toString());
+		wri.append("hijk", 1, 4);
+		assertEquals("abcdegijk", wri.toString());
 		wri.unwrite(20);
 		assertEquals(0, wri.length());
 	}

junit/io/sf/carte/util/DefaultSimpleWriterTest.java

@@ -0,0 +1,44 @@
+/*
+
+ Copyright (c) 2005-2025, Carlos Amengual.
+
+ SPDX-License-Identifier: BSD-3-Clause
+
+ Licensed under a BSD-style License. You can find the license here:
+ https://css4j.github.io/LICENSE.txt
+
+ */
+
+package io.sf.carte.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+import org.junit.jupiter.api.Test;
+
+public class DefaultSimpleWriterTest {
+
+	@Test
+	public void testDefaultSimpleWriter() throws IOException {
+		StringWriter writer = new StringWriter();
+		DefaultSimpleWriter wri = new DefaultSimpleWriter(writer);
+		wri.write('a');
+		wri.write("bc");
+		char[] cbuf = {'d', 'e', 'f'};
+		wri.write(cbuf , 0, cbuf.length);
+		wri.write(1);
+		wri.write(0);
+		assertEquals("abcdef10", writer.toString());
+		wri.append("ghijk", 1, 4);
+		assertEquals("abcdef10hij", writer.toString());
+		assertThrows(UnsupportedOperationException.class, () -> wri.unwrite());
+		assertEquals("abcdef10hij", writer.toString());
+		assertThrows(UnsupportedOperationException.class, () -> wri.unwrite(3));
+		wri.append('_');
+		assertEquals("abcdef10hij_", writer.toString());
+	}
+
+}

src/io/sf/carte/util/BufferSimpleWriter.java

@@ -11,6 +11,8 @@
 
 package io.sf.carte.util;
 
+import java.io.IOException;
+
 /**
  * An implementation of {@link SimpleWriter} backed by a {@link StringBuilder}.
  */
@@ -84,13 +86,29 @@ public String toString() {
 	/**
 	 * Remove the last character found in this buffer, if any.
 	 */
+	@Override
 	public void unwrite() {
 		int len = buffer.length();
 		if (len != 0) {
 			buffer.setLength(len - 1);
 		}
 	}
 
+	/**
+	 * Get the last character processed.
+	 * 
+	 * @return the last character processed.
+	 * @throws IllegalStateException if no character was processed yet.
+	 */
+	@Override
+	public char getLastChar() throws IllegalStateException {
+		int len = buffer.length();
+		if (len == 0) {
+			throw new IllegalStateException();
+		}
+		return buffer.charAt(len - 1);
+	}
+
 	/**
 	 * Remove the last <code>numChars</code> characters found in this buffer.
 	 * <p>
@@ -99,6 +117,7 @@ public void unwrite() {
 	 * 
 	 * @param numChars the number of characters to remove.
 	 */
+	@Override
 	public void unwrite(int numChars) {
 		int len = buffer.length() - numChars;
 		if (len < 0) {
@@ -112,6 +131,12 @@ public void write(CharSequence s) {
 		buffer.append(s);
 	}
 
+	@Override
+	public BufferSimpleWriter append(CharSequence csq, int start, int end) throws IOException {
+		buffer.append(csq, start, end);
+		return this;
+	}
+
 	@Override
 	public void write(char[] cbuf, int offset, int len) {
 		buffer.append(cbuf, offset, len);

src/io/sf/carte/util/DefaultSimpleWriter.java

@@ -0,0 +1,74 @@
+/*
+
+ Copyright (c) 2005-2025, Carlos Amengual.
+
+ SPDX-License-Identifier: BSD-3-Clause
+
+ Licensed under a BSD-style License. You can find the license here:
+ https://css4j.github.io/LICENSE.txt
+
+ */
+
+package io.sf.carte.util;
+
+import java.io.IOException;
+import java.io.Writer;
+
+/**
+ * An implementation of {@link SimpleWriter} backed by a {@link Writer}.
+ */
+public class DefaultSimpleWriter implements SimpleWriter {
+
+	private final Writer writer;
+
+	/**
+	 * Initializes a <code>BufferSimpleWriter</code> with a writer.
+	 * 
+	 * @param writer the writer.
+	 */
+	public DefaultSimpleWriter(Writer writer) {
+		super();
+		this.writer = writer;
+	}
+
+	/**
+	 * Get the {@code Writer}.
+	 * 
+	 * @return the writer.
+	 */
+	public Writer getWriter() {
+		return writer;
+	}
+
+	@Override
+	public void newLine() throws IOException {
+		writer.append('\n');
+	}
+
+	@Override
+	public void write(CharSequence s) throws IOException {
+		writer.append(s);
+	}
+
+	@Override
+	public void write(char[] cbuf, int offset, int len) throws IOException {
+		writer.write(cbuf, offset, len);
+	}
+
+	@Override
+	public DefaultSimpleWriter append(CharSequence csq, int start, int end) throws IOException {
+		writer.append(csq, start, end);
+		return this;
+	}
+
+	@Override
+	public void write(char c) throws IOException {
+		writer.append(c);
+	}
+
+	@Override
+	public void write(int num) throws IOException {
+		writer.write(Integer.toString(num));
+	}
+
+}

src/io/sf/carte/util/SimpleWriter.java

@@ -22,7 +22,7 @@
  * instead may target another system.
  *
  */
-public interface SimpleWriter {
+public interface SimpleWriter extends Appendable {
 
 	/**
 	 * Write a newline according to the characteristics of the target platform.
@@ -40,6 +40,21 @@ public interface SimpleWriter {
 	 */
 	void write(CharSequence seq) throws IOException;
 
+	@Override
+	default SimpleWriter append(CharSequence csq) throws IOException {
+		write(csq);
+		return this;
+	}
+
+	@Override
+	default SimpleWriter append(CharSequence csq, int start, int end) throws IOException {
+		if (csq == null) {
+			csq = "null";
+		}
+		write(csq.subSequence(start, end));
+		return this;
+	}
+
 	/**
 	 * Write a sequence of characters from an array.
 	 * 
@@ -64,6 +79,12 @@ public interface SimpleWriter {
 	 */
 	void write(char c) throws IOException;
 
+	@Override
+	default SimpleWriter append(char c) throws IOException {
+		write(c);
+		return this;
+	}
+
 	/**
 	 * Write an integer.
 	 * 
@@ -72,6 +93,47 @@ public interface SimpleWriter {
 	 * @throws IOException
 	 *             if an error happens when writing.
 	 */
-	void write(int num) throws IOException;
+	default void write(int num) throws IOException {
+		write(Integer.toString(num));
+	}
+
+	/**
+	 * Remove the last character found in this buffer, if any.
+	 * <p>
+	 * Optional operation.
+	 * </p>
+	 * 
+	 * @throws UnsupportedOperationException if the operation is not supported.
+	 */
+	default void unwrite() throws UnsupportedOperationException {
+		throw new UnsupportedOperationException("Cannot unwrite.");
+	}
+
+	/**
+	 * Remove the last <code>numChars</code> characters found in this buffer.
+	 * <p>
+	 * If <code>numChars</code> is larger than the length of this buffer, removes
+	 * all its contents.
+	 * 
+	 * @param numChars the number of characters to remove.
+	 * @throws UnsupportedOperationException if the operation is not supported.
+	 */
+	default void unwrite(int numChars) throws UnsupportedOperationException {
+		throw new UnsupportedOperationException("Cannot unwrite.");
+	}
+
+	/**
+	 * Get the last character processed.
+	 * <p>
+	 * Optional operation.
+	 * </p>
+	 * 
+	 * @return the last character processed.
+	 * @throws UnsupportedOperationException if the operation is not supported.
+	 * @throws IllegalStateException         if no character was processed yet.
+	 */
+	default char getLastChar() throws UnsupportedOperationException, IllegalStateException {
+		throw new UnsupportedOperationException("Cannot retrieve the last character.");
+	}
 
 }