quick sketch of java/io/*

classpath/java/io/IOException.java

@@ -0,0 +1,19 @@
+package java.io;
+
+public class IOException extends Exception {
+  public IOException(String message, Throwable cause) {
+    super(message, cause);
+  }
+
+  public IOException(String message) {
+    this(message, null);
+  }
+
+  public IOException(Throwable cause) {
+    this(null, cause);
+  }
+
+  public IOException() {
+    this(null, null);
+  }
+}