### Question:
EntityTagHeaderProvider implements HeaderDelegate<EntityTag> { public EntityTag fromString(String header) { if (header == null) { throw new IllegalArgumentException("ETag value can not be null"); } if ("*".equals(header)) { return new EntityTag("*"); } String tag = null; boolean weak = false; int i = header.indexOf(WEAK_PREFIX); if (i != -1) { weak = true; if (i + 2 < header.length()) { tag = header.substring(i + 2); } else { return new EntityTag("", weak); } } else { tag = header; } if (tag.length() > 0 && !tag.startsWith("\"") && !tag.endsWith("\"")) { return new EntityTag(tag, weak); } if (tag.length() < 2 || !tag.startsWith("\"") || !tag.endsWith("\"")) { throw new IllegalArgumentException("Misformatted ETag : " + header); } tag = tag.length() == 2 ? "" : tag.substring(1, tag.length() - 1); return new EntityTag(tag, weak); }  EntityTag fromString(String header); String toString(EntityTag tag);  }### Answer:
@Test public void testFromString() { EntityTag tag = EntityTag.valueOf("\"\""); assertFalse(tag.isWeak() && "".equals(tag.getValue())); tag = EntityTag.valueOf("W/"); assertTrue(tag.isWeak() && "".equals(tag.getValue())); tag = EntityTag.valueOf("W/\"12345\""); assertTrue(tag.isWeak() && "12345".equals(tag.getValue())); tag = EntityTag.valueOf("\"12345\""); assertFalse(tag.isWeak() && "12345".equals(tag.getValue())); }
@Test public void testFromString() { EntityTag tag = EntityTag.valueOf("\"\""); assertTrue(!tag.isWeak() && "".equals(tag.getValue())); tag = EntityTag.valueOf("W/"); assertTrue(tag.isWeak() && "".equals(tag.getValue())); tag = EntityTag.valueOf("W/\"12345\""); assertTrue(tag.isWeak() && "12345".equals(tag.getValue())); tag = EntityTag.valueOf("\"12345\""); assertTrue(!tag.isWeak() && "12345".equals(tag.getValue())); }