Allow null for input/output strings and chars.

Rearrange JARs.

.classpath

@@ -4,8 +4,8 @@
 	<classpathentry excluding="**/.svn/*" kind="src" path="test"/>
 	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
 	<classpathentry kind="lib" path="build/junit-4.6.jar"/>
-	<classpathentry exported="true" kind="lib" path="lib/minlog-1.2.jar"/>
-	<classpathentry exported="true" kind="lib" path="lib/asm-3.3.1.jar"/>
-	<classpathentry exported="true" kind="lib" path="lib/reflectasm-1.01.jar"/>
+	<classpathentry kind="lib" path="lib/optional/asm-3.3.1.jar"/>
+	<classpathentry kind="lib" path="lib/optional/reflectasm-1.01.jar"/>
+	<classpathentry kind="lib" path="lib/minlog-1.2.jar"/>
 	<classpathentry kind="output" path="bin"/>
 </classpath>

project.yaml

@@ -1,7 +1,4 @@
-version: 2.01
-dependencies:
-- ../reflectasm
-- ../minlog
+version: 2.02
 ---
 Build.build(project);
-Build.oneJAR(project);
+Build.oneJAR(project);

src/com/esotericsoftware/kryo/io/Input.java

@@ -344,7 +344,13 @@ public boolean canReadInt () throws KryoException {
 	/** Reads the length and string of 8 bit characters. */
 	public String readChars () throws KryoException {
 		int charCount = readInt(true);
-		if (charCount == 0) return "";
+		switch (charCount) {
+		case 0:
+			return null;
+		case 1:
+			return "";
+		}
+		charCount--;
 		if (chars.length < charCount) chars = new char[charCount];
 		if (charCount > require(1, charCount)) return readChars_slow(charCount);
 		char[] chars = this.chars;
@@ -368,7 +374,13 @@ private String readChars_slow (int charCount) {
 	/** Reads the length and string of UTF8 characters. */
 	public String readString () throws KryoException {
 		int charCount = readInt(true);
-		if (charCount == 0) return "";
+		switch (charCount) {
+		case 0:
+			return null;
+		case 1:
+			return "";
+		}
+		charCount--;
 		if (chars.length < charCount) chars = new char[charCount];
 		char[] chars = this.chars;
 		byte[] buffer = this.buffer;

src/com/esotericsoftware/kryo/io/Output.java

@@ -232,9 +232,12 @@ else if ((value >>> 21 & ~0x7F) == 0)
 
 	/** Writes the length and string using 1 byte per character. */
 	public void writeChars (String value) throws KryoException {
-		if (value == null) throw new IllegalArgumentException("value cannot be null.");
+		if (value == null) {
+			writeByte(0);
+			return;
+		}
 		int charCount = value.length();
-		writeInt(charCount, true);
+		writeInt(charCount + 1, true);
 		if (capacity < charCount)
 			writeChars_slow(value, charCount);
 		else {
@@ -257,11 +260,15 @@ private void writeChars_slow (String value, int charCount) throws KryoException
 		}
 	}
 
-	/** Writes the length and string using UTF8. */
+	/** Writes the length and string using UTF8, or null.
+	 * @param value May be null. */
 	public void writeString (String value) throws KryoException {
-		if (value == null) throw new IllegalArgumentException("value cannot be null.");
+		if (value == null) {
+			writeByte(0);
+			return;
+		}
 		int charCount = value.length();
-		writeInt(charCount, true);
+		writeInt(charCount + 1, true);
 		int charIndex = 0;
 		if (capacity >= charCount) {
 			// Try to write 8 bit chars.

test/com/esotericsoftware/kryo/InputOutputTest.java

@@ -87,22 +87,26 @@ public void runUTFTest (Output write) throws IOException {
 		write.writeString("uno");
 		write.writeString("dos");
 		write.writeString("tres");
+		write.writeString(null);
 		write.writeString(value1);
 		write.writeString(value2);
 		write.writeChars("uno");
 		write.writeChars("dos");
 		write.writeChars("tres");
+		write.writeChars(null);
 		write.writeChars(value1);
 
 		Input read = new Input(write.toBytes());
 		assertEquals("uno", read.readString());
 		assertEquals("dos", read.readString());
 		assertEquals("tres", read.readString());
+		assertEquals(null, read.readString());
 		assertEquals(value1, read.readString());
 		assertEquals(value2, read.readString());
 		assertEquals("uno", read.readChars());
 		assertEquals("dos", read.readChars());
 		assertEquals("tres", read.readChars());
+		assertEquals(null, read.readChars());
 		assertEquals(value1, read.readChars());
 	}