### Question:
StringOption extends ValueOption<StringOption> { public boolean isEmpty() { if (nullValue) { throw new NullPointerException(); } return entity.getLength() == 0; } StringOption();  StringOption(String textOrNull); Text get(); String getAsString(); StringBuilder appendTo(StringBuilder buffer); boolean isEmpty(); Text or(Text alternate); String or(String alternate); void reset(); @Deprecated StringOption modify(Text newText); @Deprecated StringOption modify(String newText); @Deprecated StringOption modify(byte[] utf8, int offset, int length); @Override @Deprecated void copyFrom(StringOption optionOrNull); @Override int hashCode(); @Override boolean equals(Object obj); boolean has(String other); boolean has(Text other); boolean contains(String sub); boolean contains(StringOption sub); boolean startsWith(String prefix); boolean startsWith(StringOption prefix); boolean endsWith(String suffix); boolean endsWith(StringOption suffix); @Override int compareTo(WritableRawComparable o); @Override String toString(); @Override void write(DataOutput out); @SuppressWarnings("deprecation") @Override void readFields(DataInput in); @SuppressWarnings("deprecation") @Override int restore(byte[] bytes, int offset, int limit); @Override int getSizeInBytes(byte[] buf, int offset); @Override int compareInBytes(byte[] b1, int o1, byte[] b2, int o2); static int getBytesLength(byte[] bytes, int offset, int length); static int compareBytes(
            byte[] b1, int s1, int l1,
            byte[] b2, int s2, int l2);  }### Answer:
@Test public void is_empty() { npe(() -> new StringOption().isEmpty()); assertThat(new StringOption("").isEmpty(), is(true)); assertThat(new StringOption("Hello, world!").isEmpty(), is(false)); assertThat(new StringOption(" ").isEmpty(), is(false)); }