Step 1: resize() should work for capacity 0.

src/main/java/com/github/tommyettinger/ds/BooleanDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final boolean[] newArray = new boolean[newSize];
+		final boolean[] newArray = new boolean[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/ByteDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final byte[] newArray = new byte[newSize];
+		final byte[] newArray = new byte[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/CharDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final char[] newArray = new char[newSize];
+		final char[] newArray = new char[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/DoubleDeque.java

@@ -203,7 +203,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final double[] newArray = new double[newSize];
+		final double[] newArray = new double[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/FloatDeque.java

@@ -203,7 +203,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final float[] newArray = new float[newSize];
+		final float[] newArray = new float[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/IntDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final int[] newArray = new int[newSize];
+		final int[] newArray = new int[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/LongDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final long[] newArray = new long[newSize];
+		final long[] newArray = new long[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/main/java/com/github/tommyettinger/ds/ShortDeque.java

@@ -202,7 +202,7 @@ protected void resize (int newSize) {
 		final int head = this.head;
 		final int tail = this.tail;
 
-		final short[] newArray = new short[newSize];
+		final short[] newArray = new short[Math.max(1, newSize)];
 		if (head < tail) {
 			// Continuous
 			System.arraycopy(values, head, newArray, 0, tail - head);

src/test/java/com/github/tommyettinger/ds/test/ConstructionTest.java

@@ -40,8 +40,7 @@ public void testObjectEmpty() {
 
 		ObjectDeque<String> deque = new ObjectDeque<>(0);
 		deque.add("START");
-		deque.remove();
-		deque.addAll(list);
+		deque.addAll(names);
 		Assert.assertEquals(targetLength, deque.size());
 
 		ObjectSet<String> set = new ObjectSet<>(0);