FieldPosition is a simple class used by Format
+ * and its subclasses to identify fields in formatted output. Fields can
+ * be identified in two ways:
+ * _FIELD. The constants are defined in the various
+ * subclasses of Format.
+ * Format.Field constant, see ERA_FIELD
+ * and its friends in DateFormat for an example.
+ *
+ * FieldPosition keeps track of the position of the
+ * field within the formatted output with two indices: the index
+ * of the first character of the field and the index of the last
+ * character of the field.
+ *
+ *
+ * One version of the format method in the various
+ * Format classes requires a FieldPosition
+ * object as an argument. You use this format method
+ * to perform partial formatting or to get information about the
+ * formatted output (such as the position of a field).
+ *
+ *
+ * If you are interested in the positions of all attributes in the
+ * formatted string use the Format method
+ * formatToCharacterIterator.
+ *
+ * @author Mark Davis
+ * @see java.text.Format
+ */
+public class FieldPosition {
+
+ /**
+ * Input: Desired field to determine start and end offsets for.
+ * The meaning depends on the subclass of Format.
+ */
+ int field = 0;
+
+ /**
+ * Output: End offset of field in text.
+ * If the field does not occur in the text, 0 is returned.
+ */
+ int endIndex = 0;
+
+ /**
+ * Output: Start offset of field in text.
+ * If the field does not occur in the text, 0 is returned.
+ */
+ int beginIndex = 0;
+
+ /**
+ * Desired field this FieldPosition is for.
+ */
+ private Format.Field attribute;
+
+ /**
+ * Creates a FieldPosition object for the given field. Fields are
+ * identified by constants, whose names typically end with _FIELD,
+ * in the various subclasses of Format.
+ *
+ * @see java.text.NumberFormat#INTEGER_FIELD
+ * @see java.text.NumberFormat#FRACTION_FIELD
+ * @see java.text.DateFormat#YEAR_FIELD
+ * @see java.text.DateFormat#MONTH_FIELD
+ */
+ public FieldPosition(int field) {
+ this.field = field;
+ }
+
+ /**
+ * Creates a FieldPosition object for the given field constant. Fields are
+ * identified by constants defined in the various Format
+ * subclasses. This is equivalent to calling
+ * new FieldPosition(attribute, -1).
+ *
+ * @param attribute Format.Field constant identifying a field
+ * @since 1.4
+ */
+ public FieldPosition(Format.Field attribute) {
+ this(attribute, -1);
+ }
+
+ /**
+ * Creates a FieldPosition object for the given field.
+ * The field is identified by an attribute constant from one of the
+ * Field subclasses as well as an integer field ID
+ * defined by the Format subclasses. Format
+ * subclasses that are aware of Field should give precedence
+ * to attribute and ignore fieldID if
+ * attribute is not null. However, older Format
+ * subclasses may not be aware of Field and rely on
+ * fieldID. If the field has no corresponding integer
+ * constant, fieldID should be -1.
+ *
+ * @param attribute Format.Field constant identifying a field
+ * @param fieldID integer constantce identifying a field
+ * @since 1.4
+ */
+ public FieldPosition(Format.Field attribute, int fieldID) {
+ this.attribute = attribute;
+ this.field = fieldID;
+ }
+
+ /**
+ * Returns the field identifier as an attribute constant
+ * from one of the Field subclasses. May return null if
+ * the field is specified only by an integer field ID.
+ *
+ * @return Identifier for the field
+ * @since 1.4
+ */
+ public Format.Field getFieldAttribute() {
+ return attribute;
+ }
+
+ /**
+ * Retrieves the field identifier.
+ */
+ public int getField() {
+ return field;
+ }
+
+ /**
+ * Retrieves the index of the first character in the requested field.
+ */
+ public int getBeginIndex() {
+ return beginIndex;
+ }
+
+ /**
+ * Retrieves the index of the character following the last character in the
+ * requested field.
+ */
+ public int getEndIndex() {
+ return endIndex;
+ }
+
+ /**
+ * Sets the begin index. For use by subclasses of Format.
+ * @since 1.2
+ */
+ public void setBeginIndex(int bi) {
+ beginIndex = bi;
+ }
+
+ /**
+ * Sets the end index. For use by subclasses of Format.
+ * @since 1.2
+ */
+ public void setEndIndex(int ei) {
+ endIndex = ei;
+ }
+
+ /**
+ * Returns a Format.FieldDelegate instance that is associated
+ * with the FieldPosition. When the delegate is notified of the same
+ * field the FieldPosition is associated with, the begin/end will be
+ * adjusted.
+ */
+ Format.FieldDelegate getFieldDelegate() {
+ return new Delegate();
+ }
+
+ /**
+ * Overrides equals
+ */
+ public boolean equals(Object obj)
+ {
+ if (obj == null) return false;
+ if (!(obj instanceof FieldPosition))
+ return false;
+ FieldPosition other = (FieldPosition) obj;
+ if (attribute == null) {
+ if (other.attribute != null) {
+ return false;
+ }
+ }
+ else if (!attribute.equals(other.attribute)) {
+ return false;
+ }
+ return (beginIndex == other.beginIndex
+ && endIndex == other.endIndex
+ && field == other.field);
+ }
+
+ /**
+ * Returns a hash code for this FieldPosition.
+ * @return a hash code value for this object
+ */
+ public int hashCode() {
+ return (field << 24) | (beginIndex << 16) | endIndex;
+ }
+
+ /**
+ * Return a string representation of this FieldPosition.
+ * @return a string representation of this object
+ */
+ public String toString() {
+ return getClass().getName() +
+ "[field=" + field + ",attribute=" + attribute +
+ ",beginIndex=" + beginIndex +
+ ",endIndex=" + endIndex + ']';
+ }
+
+
+ /**
+ * Return true if the receiver wants a Format.Field value and
+ * attribute is equal to it.
+ */
+ private boolean matchesField(Format.Field attribute) {
+ if (this.attribute != null) {
+ return this.attribute.equals(attribute);
+ }
+ return false;
+ }
+
+ /**
+ * Return true if the receiver wants a Format.Field value and
+ * attribute is equal to it, or true if the receiver
+ * represents an inteter constant and field equals it.
+ */
+ private boolean matchesField(Format.Field attribute, int field) {
+ if (this.attribute != null) {
+ return this.attribute.equals(attribute);
+ }
+ return (field == this.field);
+ }
+
+
+ /**
+ * An implementation of FieldDelegate that will adjust the begin/end
+ * of the FieldPosition if the arguments match the field of
+ * the FieldPosition.
+ */
+ private class Delegate implements Format.FieldDelegate {
+ /**
+ * Indicates whether the field has been encountered before. If this
+ * is true, and formatted is invoked, the begin/end
+ * are not updated.
+ */
+ private boolean encounteredField;
+
+ public void formatted(Format.Field attr, Object value, int start,
+ int end, StringBuffer buffer) {
+ if (!encounteredField && matchesField(attr)) {
+ setBeginIndex(start);
+ setEndIndex(end);
+ encounteredField = (start != end);
+ }
+ }
+
+ public void formatted(int fieldID, Format.Field attr, Object value,
+ int start, int end, StringBuffer buffer) {
+ if (!encounteredField && matchesField(attr, fieldID)) {
+ setBeginIndex(start);
+ setEndIndex(end);
+ encounteredField = (start != end);
+ }
+ }
+ }
+}