flesh out classpath enough to test threading; fix indexing bug in parsePool()

classpath/java/lang/StringBuilder.java

@@ -0,0 +1,42 @@
+package java.lang;
+
+public class StringBuilder {
+  private Cell chain;
+  private int length;
+
+  public StringBuilder append(String s) {
+    chain = new Cell(s, chain);
+    length += s.length();
+    return this;
+  }
+
+  public StringBuilder append(int v) {
+    append(String.valueOf(v));
+    return this;
+  }
+
+  public StringBuilder append(long v) {
+    append(String.valueOf(v));
+    return this;
+  }
+
+  public String toString() {
+    char[] array = new char[length];
+    int index = length;
+    for (Cell c = chain; c != null; c = c.next) {
+      index -= c.value.length();
+      c.value.getChars(0, c.value.length(), array, index);
+    }
+    return vm.Strings.wrap(array, 0, array.length);
+  }
+
+  private static class Cell {
+    public final String value;
+    public final Cell next;
+
+    public Cell(String value, Cell next) {
+      this.value = value;
+      this.next = next;
+    }
+  }
+}