Create a string set preference for {@code key}. Default is an empty set. Note that returned set
value will always be unmodifiable.
504255
@RequiresApi(HONEYCOMB)
  @CheckResult @NonNull
  public Preference<Set<String>> getStringSet(@NonNull String key) {
    return getStringSet(key, Collections.<String>emptySet());
  }
751089
public String[] getStringsWithDefault(String key, String[] defaultValue) {
		String[] value = getStrings(key, null);
		if (null == value) {
			value = defaultValue;
		}

		return value;
	}
1034312
public String getProperty(String key, String defaultValue) {
        String value = getProperty(key, String.class);
        return StringUtils.isEmpty(value) ? defaultValue : value;
    }
1305846
public void setString(@NotNull final String key, @NotNull final String value) {
        props.setProperty(key, value);
        LOGGER.debug("Setting: {}='{}'", key, value);
    }
895630
public Set<String> getPropAsCaseInsensitiveSet(String key) {
    return ImmutableSortedSet.copyOf(String.CASE_INSENSITIVE_ORDER, LIST_SPLITTER.split(getProp(key)));
  }
965220
public String optString(String key, String defaultValue) {
        Object object = this.opt(key);
        return NULL.equals(object) ? defaultValue : object.toString();
    }
285496
public Object opt(String key) {
		return key == null ? null : this.fields.get(key);
	}
1346570
public JsonWriter keyUnescaped(CharSequence key) {
        startKey();

        if (key == null) {
            throw new IllegalArgumentException("Expected map key, but got null.");
        }

        writer.write('\"');
        writer.write(key.toString());
        writer.write('\"');
        writer.write(':');
        return this;

    }
1247352
@SuppressWarnings("null")
	public static String value(String key, String defaultValue) {
		return System.getProperty(key, defaultValue);
	}
7785
@Override
    public String getString( final String      key,
                             final String      defaultValue )
    {
        String  candidate;
        candidate = getFormattedPropValue( key );

        if ( candidate == null )
        {
            return defaultValue;
        }

        return candidate;
    }
505438
public String getString(String key) {
		if (key == null || key.isEmpty()) {
			return null;
		}
		String property = null;
		for (ConfigurationSource configurationSource : configurationSources) {
			property = configurationSource.getValue(key);
			if (property != null) {
				break;
			}
		}
		return property;
	}
136629
@NonNull
    @Override
    public MutableDocument setString(@NonNull String key, String value) {
        return setValue(key, value);
    }
267090
public Object set(String key, Object value) {
        int idx = keys.indexOf(key);
        if (idx == -1) {
            keys.add(key);
            values.add(value);
            return null;
        }
        return values.set(idx, value);
    }
783410
public String optString(String key, String defaultValue) {
    Object o = opt(key);
    return o != null ? o.toString() : defaultValue;
  }
505361
public T getValueByString(String key) {
        for (T value : values) {
            if (keyFactory.generateKey(value).equals(key)) {
                return value;
            }
        }
        return null;
    }
1122551
public MemberConfig setProperty(String key, String value) {
    this.properties.put(key, value);
    return this;
  }
1293771
public String optString(Enum<?> key, String defaultValue) {
		return optString(key.name(), defaultValue);
	}