Added several useful classes

classpath/java/io/ByteArrayInputStream.java

@@ -0,0 +1,25 @@
+package java.io;
+
+public class ByteArrayInputStream extends InputStream {
+  private final byte[] array;
+  private int position;
+  private final int length;
+
+  public ByteArrayInputStream(byte[] array, int offset, int length) {
+    this.array = array;
+    position = offset;
+    this.length = length;
+  }
+
+  public int read() {
+    if (position < length) {
+      return array[position++] & 0xff;
+    } else {
+      return -1;
+    }
+  }
+
+  public int available() {
+    returns length - position;
+  }
+}