StdDateFormat.java
package com.fasterxml.jackson.databind.util;
import java.text.DateFormat;
import java.text.FieldPosition;
import java.text.ParseException;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import com.fasterxml.jackson.core.io.NumberInput;
/**
* Jackson's internal {@link DateFormat} implementation used by standard Date
* serializers and deserializers to implement default behavior: does <b>NOT</b>
* fully implement all aspects expected by {@link DateFormat} and as a consequence
* <b>SHOULD NOT</b> to be used by code outside core Jackson databind functionality.
* In particular, {@code ParsePosition} argument of {@link #parse(String, ParsePosition)}
* and {@link #format(Date, StringBuffer, FieldPosition)} methods is fully ignored;
* Jackson itself never calls these methods.
*<p>
* For serialization defaults to using
* an ISO-8601 compliant format (format String "yyyy-MM-dd'T'HH:mm:ss.SSSZ")
* and for deserialization, both ISO-8601 and RFC-1123.
*<br>
* Note that `Z` in format String refers to ISO-8601 time offset notation which produces
* values like "-08:00" -- that is, full minute/hour combo without colon, and not using `Z`
* as alias for "+00:00".
* Inclusion of colon as separator, as default setting, started in Jackson 2.11:
* prior versions omitted it.
* Note that it is possible to enable/disable use of colon in time offset by using method
* {@link #withColonInTimeZone} for creating new differently configured format instance,
* and configuring {@code ObjectMapper} with it.
*<p>
* TODO: in Jackson 2.14 or later, should change behavior to fail if {@link ParsePosition}
* is specified by caller (at least with non-0 offset).
*/
@SuppressWarnings("serial")
public class StdDateFormat
extends DateFormat
{
/* 24-Jun-2017, tatu: Finally rewrote deserialization to use basic Regex
* instead of SimpleDateFormat; partly for better concurrency, partly
* for easier enforcing of specific rules. Heavy lifting done by Calendar,
* anyway.
*/
protected final static String PATTERN_PLAIN_STR = "\\d\\d\\d\\d[-]\\d\\d[-]\\d\\d";
protected final static Pattern PATTERN_PLAIN = Pattern.compile(PATTERN_PLAIN_STR);
protected final static Pattern PATTERN_ISO8601;
static {
Pattern p = null;
try {
p = Pattern.compile(PATTERN_PLAIN_STR
+"[T]\\d\\d[:]\\d\\d(?:[:]\\d\\d)?" // hours, minutes, optional seconds
+"(\\.\\d+)?" // optional second fractions
+"(Z|[+-]\\d\\d(?:[:]?\\d\\d)?)?" // optional timeoffset/Z
);
} catch (Exception t) {
throw new RuntimeException(t);
}
PATTERN_ISO8601 = p;
}
/**
* Defines a commonly used date format that conforms
* to ISO-8601 date formatting standard, when it includes basic undecorated
* timezone definition.
*/
public final static String DATE_FORMAT_STR_ISO8601 = "yyyy-MM-dd'T'HH:mm:ss.SSSX";
/**
* ISO-8601 with just the Date part, no time: needed for error messages
*/
protected final static String DATE_FORMAT_STR_PLAIN = "yyyy-MM-dd";
/**
* This constant defines the date format specified by
* RFC 1123 / RFC 822. Used for parsing via `SimpleDateFormat` as well as
* error messages.
*/
protected final static String DATE_FORMAT_STR_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";
/**
* For error messages we'll also need a list of all formats.
*/
protected final static String[] ALL_FORMATS = new String[] {
DATE_FORMAT_STR_ISO8601,
"yyyy-MM-dd'T'HH:mm:ss.SSS", // ISO-8601 but no timezone
DATE_FORMAT_STR_RFC1123,
DATE_FORMAT_STR_PLAIN
};
/**
* By default we use UTC for everything, with Jackson 2.7 and later
* (2.6 and earlier relied on GMT)
*/
protected final static TimeZone DEFAULT_TIMEZONE;
static {
DEFAULT_TIMEZONE = TimeZone.getTimeZone("UTC"); // since 2.7
}
protected final static Locale DEFAULT_LOCALE = Locale.US;
protected final static DateFormat DATE_FORMAT_RFC1123;
/* Let's construct "blueprint" date format instances: cannot be used
* as is, due to thread-safety issues, but can be used for constructing
* actual instances more cheaply (avoids re-parsing).
*/
static {
// Another important thing: let's force use of default timezone for
// baseline DataFormat objects
DATE_FORMAT_RFC1123 = new SimpleDateFormat(DATE_FORMAT_STR_RFC1123, DEFAULT_LOCALE);
DATE_FORMAT_RFC1123.setTimeZone(DEFAULT_TIMEZONE);
}
/**
* A singleton instance can be used for cloning purposes, as a blueprint of sorts.
*/
public final static StdDateFormat instance = new StdDateFormat();
/**
* Blueprint "Calendar" instance for use during formatting. Cannot be used as is,
* due to thread-safety issues, but can be used for constructing actual instances
* more cheaply by cloning.
*
* @since 2.9.1
*/
protected static final Calendar CALENDAR = new GregorianCalendar(DEFAULT_TIMEZONE, DEFAULT_LOCALE);
/**
* Caller may want to explicitly override timezone to use; if so,
* we will have non-null value here.
*/
protected transient TimeZone _timezone;
protected final Locale _locale;
/**
* Explicit override for leniency, if specified.
*<p>
* Cannot be `final` because {@link #setLenient(boolean)} returns
* `void`.
*
* @since 2.7
*/
protected Boolean _lenient;
/**
* Lazily instantiated calendar used by this instance for serialization ({@link #format(Date)}).
*
* @since 2.9.1
*/
private transient Calendar _calendar;
private transient DateFormat _formatRFC1123;
/**
* Whether the TZ offset must be formatted with a colon between hours and minutes ({@code HH:mm} format)
*<p>
* Defaults to {@code true} since 2.11: earlier versions defaulted to {@code false}
* for backwards compatibility reasons
*
* @since 2.9.1
*/
private boolean _tzSerializedWithColon = true;
/*
/**********************************************************
/* Life cycle, accessing singleton "standard" formats
/**********************************************************
*/
public StdDateFormat() {
_locale = DEFAULT_LOCALE;
}
@Deprecated // since 2.7
public StdDateFormat(TimeZone tz, Locale loc) {
_timezone = tz;
_locale = loc;
}
protected StdDateFormat(TimeZone tz, Locale loc, Boolean lenient) {
this(tz, loc, lenient, false);
}
/**
* @since 2.9.1
*/
protected StdDateFormat(TimeZone tz, Locale loc, Boolean lenient,
boolean formatTzOffsetWithColon) {
_timezone = tz;
_locale = loc;
_lenient = lenient;
_tzSerializedWithColon = formatTzOffsetWithColon;
}
public static TimeZone getDefaultTimeZone() {
return DEFAULT_TIMEZONE;
}
/**
* Method used for creating a new instance with specified timezone;
* if no timezone specified, defaults to the default timezone (UTC).
*/
public StdDateFormat withTimeZone(TimeZone tz) {
if (tz == null) {
tz = DEFAULT_TIMEZONE;
}
if ((tz == _timezone) || tz.equals(_timezone)) {
return this;
}
return new StdDateFormat(tz, _locale, _lenient, _tzSerializedWithColon);
}
/**
* "Mutant factory" method that will return an instance that uses specified
* {@code Locale}:
* either {@code this} instance (if setting would not change), or newly
* constructed instance with different {@code Locale} to use.
*/
public StdDateFormat withLocale(Locale loc) {
if (loc.equals(_locale)) {
return this;
}
return new StdDateFormat(_timezone, loc, _lenient, _tzSerializedWithColon);
}
/**
* "Mutant factory" method that will return an instance that has specified leniency
* setting: either {@code this} instance (if setting would not change), or newly
* constructed instance.
*
* @since 2.9
*/
public StdDateFormat withLenient(Boolean b) {
if (_equals(b, _lenient)) {
return this;
}
return new StdDateFormat(_timezone, _locale, b, _tzSerializedWithColon);
}
/**
* "Mutant factory" method that will return an instance that has specified
* handling of colon when serializing timezone (timezone either written
* like {@code +0500} or {@code +05:00}):
* either {@code this} instance (if setting would not change), or newly
* constructed instance with desired setting for colon inclusion.
*<p>
* NOTE: does NOT affect deserialization as colon is optional accepted
* but not required -- put another way, either serialization is accepted
* by this class.
*
* @since 2.9.1
*/
public StdDateFormat withColonInTimeZone(boolean b) {
if (_tzSerializedWithColon == b) {
return this;
}
return new StdDateFormat(_timezone, _locale, _lenient, b);
}
@Override
public StdDateFormat clone() {
// Although there isn't that much state to share, we do need to
// orchestrate a bit, mostly since timezones may be changed
return new StdDateFormat(_timezone, _locale, _lenient, _tzSerializedWithColon);
}
/**
* Method for getting a non-shared DateFormat instance
* that uses specified timezone and can handle simple ISO-8601
* compliant date format.
*
* @since 2.4
*
* @deprecated Since 2.9
*/
@Deprecated // since 2.9
public static DateFormat getISO8601Format(TimeZone tz, Locale loc) {
DateFormat df = new SimpleDateFormat(DATE_FORMAT_STR_ISO8601, loc);
df.setTimeZone(DEFAULT_TIMEZONE);
return df;
}
/**
* Method for getting a non-shared DateFormat instance
* that uses specific timezone and can handle RFC-1123
* compliant date format.
*
* @since 2.4
*
* @deprecated Since 2.9
*/
@Deprecated // since 2.9
public static DateFormat getRFC1123Format(TimeZone tz, Locale loc) {
return _cloneFormat(DATE_FORMAT_RFC1123, DATE_FORMAT_STR_RFC1123,
tz, loc, null);
}
/*
/**********************************************************
/* Public API, configuration
/**********************************************************
*/
@Override // since 2.6
public TimeZone getTimeZone() {
return _timezone;
}
@Override
public void setTimeZone(TimeZone tz)
{
// DateFormats are timezone-specific (via Calendar contained),
// so need to reset instances if timezone changes:
if (!tz.equals(_timezone)) {
_clearFormats();
_timezone = tz;
}
}
/**
* Need to override since we need to keep track of leniency locally,
* and not via underlying {@link Calendar} instance like base class
* does.
*/
@Override // since 2.7
public void setLenient(boolean enabled) {
Boolean newValue = Boolean.valueOf(enabled);
if (!_equals(newValue, _lenient)) {
_lenient = newValue;
// and since leniency settings may have been used:
_clearFormats();
}
}
@Override // since 2.7
public boolean isLenient() {
// default is, I believe, true
return (_lenient == null) || _lenient.booleanValue();
}
/**
* Accessor for checking whether this instance would include colon
* within timezone serialization or not: if {code true}, timezone offset
* is serialized like {@code -06:00}; if {code false} as {@code -0600}.
*<p>
* NOTE: only relevant for serialization (formatting), as deserialization
* (parsing) always accepts optional colon but does not require it, regardless
* of this setting.
*
* @return {@code true} if a colon is to be inserted between the hours and minutes
* of the TZ offset when serializing as String; otherwise {@code false}
*
* @since 2.9.1
*/
public boolean isColonIncludedInTimeZone() {
return _tzSerializedWithColon;
}
/*
/**********************************************************
/* Public API, parsing
/**********************************************************
*/
@Override
public Date parse(String dateStr) throws ParseException
{
dateStr = dateStr.trim();
ParsePosition pos = new ParsePosition(0);
Date dt = _parseDate(dateStr, pos);
if (dt != null) {
return dt;
}
StringBuilder sb = new StringBuilder();
for (String f : ALL_FORMATS) {
if (sb.length() > 0) {
sb.append("\", \"");
} else {
sb.append('"');
}
sb.append(f);
}
sb.append('"');
throw new ParseException
(String.format("Cannot parse date \"%s\": not compatible with any of standard forms (%s)",
dateStr, sb.toString()), pos.getErrorIndex());
}
// 24-Jun-2017, tatu: I don't think this ever gets called. So could... just not implement?
@Override
public Date parse(String dateStr, ParsePosition pos)
{
try {
return _parseDate(dateStr, pos);
} catch (ParseException e) {
// may look weird but this is what `DateFormat` suggest to do...
}
return null;
}
protected Date _parseDate(String dateStr, ParsePosition pos) throws ParseException
{
if (looksLikeISO8601(dateStr)) { // also includes "plain"
return parseAsISO8601(dateStr, pos);
}
// Also consider "stringified" simple time stamp
int i = dateStr.length();
while (--i >= 0) {
char ch = dateStr.charAt(i);
if (ch < '0' || ch > '9') {
// 07-Aug-2013, tatu: And [databind#267] points out that negative numbers should also work
if (i > 0 || ch != '-') {
break;
}
}
}
if ((i < 0)
// let's just assume negative numbers are fine (can't be RFC-1123 anyway); check length for positive
&& (dateStr.charAt(0) == '-' || NumberInput.inLongRange(dateStr, false))) {
return _parseDateFromLong(dateStr, pos);
}
// Otherwise, fall back to using RFC 1123. NOTE: call will NOT throw, just returns `null`
return parseAsRFC1123(dateStr, pos);
}
/*
/**********************************************************
/* Public API, writing
/**********************************************************
*/
@Override
public StringBuffer format(Date date, StringBuffer toAppendTo,
FieldPosition fieldPosition)
{
TimeZone tz = _timezone;
if (tz == null) {
tz = DEFAULT_TIMEZONE;
}
_format(tz, _locale, date, toAppendTo);
return toAppendTo;
}
protected void _format(TimeZone tz, Locale loc, Date date,
StringBuffer buffer)
{
Calendar cal = _getCalendar(tz);
cal.setTime(date);
// [databind#2167]: handle range beyond [1, 9999]
final int year = cal.get(Calendar.YEAR);
// Assuming GregorianCalendar, special handling needed for BCE (aka BC)
if (cal.get(Calendar.ERA) == GregorianCalendar.BC) {
_formatBCEYear(buffer, year);
} else {
if (year > 9999) {
// 22-Nov-2018, tatu: Handling beyond 4-digits is not well specified wrt ISO-8601, but
// it seems that plus prefix IS mandated. Padding is an open question, but since agreeement
// for max length would be needed, we ewould need to limit to arbitrary length
// like five digits (erroring out if beyond or padding to that as minimum).
// Instead, let's just print number out as is and let decoder try to make sense of it.
buffer.append('+');
}
pad4(buffer, year);
}
buffer.append('-');
pad2(buffer, cal.get(Calendar.MONTH) + 1);
buffer.append('-');
pad2(buffer, cal.get(Calendar.DAY_OF_MONTH));
buffer.append('T');
pad2(buffer, cal.get(Calendar.HOUR_OF_DAY));
buffer.append(':');
pad2(buffer, cal.get(Calendar.MINUTE));
buffer.append(':');
pad2(buffer, cal.get(Calendar.SECOND));
buffer.append('.');
pad3(buffer, cal.get(Calendar.MILLISECOND));
int offset = tz.getOffset(cal.getTimeInMillis());
if (offset != 0) {
int hours = Math.abs((offset / (60 * 1000)) / 60);
int minutes = Math.abs((offset / (60 * 1000)) % 60);
buffer.append(offset < 0 ? '-' : '+');
pad2(buffer, hours);
if( _tzSerializedWithColon ) {
buffer.append(':');
}
pad2(buffer, minutes);
} else {
// 24-Jun-2017, tatu: While `Z` would be conveniently short, older specs
// mandate use of full `+0000`
// 06-Mar-2020, tatu: Actually statement should read "for compatibility reasons"
// and not standards (unless it is wrt RFC-1123). This will change in 3.0 at latest
// formatted.append('Z');
if( _tzSerializedWithColon ) {
buffer.append("+00:00");
} else {
buffer.append("+0000");
}
}
}
protected void _formatBCEYear(StringBuffer buffer, int bceYearNoSign) {
// Ok. First of all, BCE 1 output (given as value `1` in era BCE) needs to become
// "+0000", but rest (from `2` up, in that era) need minus sign.
if (bceYearNoSign == 1) {
buffer.append("+0000");
return;
}
final int isoYear = bceYearNoSign - 1;
buffer.append('-');
// as with CE, 4 digit variant needs padding; beyond that not (although that part is
// open to debate, needs agreement with receiver)
// But `pad4()` deals with "big" numbers now so:
pad4(buffer, isoYear);
}
private static void pad2(StringBuffer buffer, int value) {
int tens = value / 10;
if (tens == 0) {
buffer.append('0');
} else {
buffer.append((char) ('0' + tens));
value -= 10 * tens;
}
buffer.append((char) ('0' + value));
}
private static void pad3(StringBuffer buffer, int value) {
int h = value / 100;
if (h == 0) {
buffer.append('0');
} else {
buffer.append((char) ('0' + h));
value -= (h * 100);
}
pad2(buffer, value);
}
private static void pad4(StringBuffer buffer, int value) {
int h = value / 100;
if (h == 0) {
buffer.append('0').append('0');
} else {
if (h > 99) { // [databind#2167]: handle above 9999 correctly
buffer.append(h);
} else {
pad2(buffer, h);
}
value -= (100 * h);
}
pad2(buffer, value);
}
/*
/**********************************************************
/* Std overrides
/**********************************************************
*/
@Override
public String toString() {
return String.format("DateFormat %s: (timezone: %s, locale: %s, lenient: %s)",
getClass().getName(), _timezone, _locale, _lenient);
}
public String toPattern() { // same as SimpleDateFormat
StringBuilder sb = new StringBuilder(100);
sb.append("[one of: '")
.append(DATE_FORMAT_STR_ISO8601)
.append("', '")
.append(DATE_FORMAT_STR_RFC1123)
.append("' (")
;
sb.append(Boolean.FALSE.equals(_lenient) ?
"strict" : "lenient")
.append(")]");
return sb.toString();
}
@Override // since 2.7[.2], as per [databind#1130]
public boolean equals(Object o) {
return (o == this);
}
@Override // since 2.7[.2], as per [databind#1130]
public int hashCode() {
return System.identityHashCode(this);
}
/*
/**********************************************************
/* Helper methods, parsing
/**********************************************************
*/
/**
* Helper method used to figure out if input looks like valid
* ISO-8601 string.
*/
protected boolean looksLikeISO8601(String dateStr)
{
if (dateStr.length() >= 7 // really need 10, but...
&& Character.isDigit(dateStr.charAt(0))
&& Character.isDigit(dateStr.charAt(3))
&& dateStr.charAt(4) == '-'
&& Character.isDigit(dateStr.charAt(5))
) {
return true;
}
return false;
}
private Date _parseDateFromLong(String longStr, ParsePosition pos) throws ParseException
{
long ts;
try {
ts = NumberInput.parseLong(longStr);
} catch (NumberFormatException e) {
throw new ParseException(String.format(
"Timestamp value %s out of 64-bit value range", longStr),
pos.getErrorIndex());
}
return new Date(ts);
}
protected Date parseAsISO8601(String dateStr, ParsePosition pos)
throws ParseException
{
try {
return _parseAsISO8601(dateStr, pos);
} catch (IllegalArgumentException e) {
throw new ParseException(String.format("Cannot parse date \"%s\", problem: %s",
dateStr, e.getMessage()),
pos.getErrorIndex());
}
}
protected Date _parseAsISO8601(String dateStr, ParsePosition bogus)
throws IllegalArgumentException, ParseException
{
final int totalLen = dateStr.length();
// actually, one short-cut: if we end with "Z", must be UTC
TimeZone tz = DEFAULT_TIMEZONE;
if ((_timezone != null) && ('Z' != dateStr.charAt(totalLen-1))) {
tz = _timezone;
}
Calendar cal = _getCalendar(tz);
cal.clear();
String formatStr;
if (totalLen <= 10) {
Matcher m = PATTERN_PLAIN.matcher(dateStr);
if (m.matches()) {
int year = _parse4D(dateStr, 0);
int month = _parse2D(dateStr, 5)-1;
int day = _parse2D(dateStr, 8);
cal.set(year, month, day, 0, 0, 0);
cal.set(Calendar.MILLISECOND, 0);
return cal.getTime();
}
formatStr = DATE_FORMAT_STR_PLAIN;
} else {
Matcher m = PATTERN_ISO8601.matcher(dateStr);
if (m.matches()) {
// Important! START with optional time zone; otherwise Calendar will explode
int start = m.start(2);
int end = m.end(2);
int len = end-start;
if (len > 1) { // 0 -> none, 1 -> 'Z'
// NOTE: first char is sign; then 2 digits, then optional colon, optional 2 digits
int offsetSecs = _parse2D(dateStr, start+1) * 3600; // hours
if (len >= 5) {
offsetSecs += _parse2D(dateStr, end-2) * 60; // minutes
}
if (dateStr.charAt(start) == '-') {
offsetSecs *= -1000;
} else {
offsetSecs *= 1000;
}
cal.set(Calendar.ZONE_OFFSET, offsetSecs);
// 23-Jun-2017, tatu: Not sure why, but this appears to be needed too:
cal.set(Calendar.DST_OFFSET, 0);
}
int year = _parse4D(dateStr, 0);
int month = _parse2D(dateStr, 5)-1;
int day = _parse2D(dateStr, 8);
// So: 10 chars for date, then `T`, so starts at 11
int hour = _parse2D(dateStr, 11);
int minute = _parse2D(dateStr, 14);
// Seconds are actually optional... so
int seconds;
if ((totalLen > 16) && dateStr.charAt(16) == ':') {
seconds = _parse2D(dateStr, 17);
} else {
seconds = 0;
}
cal.set(year, month, day, hour, minute, seconds);
// Optional milliseconds
start = m.start(1) + 1;
end = m.end(1);
int msecs = 0;
if (start >= end) { // no fractional
cal.set(Calendar.MILLISECOND, 0);
} else {
// first char is '.', but rest....
msecs = 0;
final int fractLen = end-start;
switch (fractLen) {
default: // [databind#1745] Allow longer fractions... for now, cap at nanoseconds tho
if (fractLen > 9) { // only allow up to nanos
throw new ParseException(String.format(
"Cannot parse date \"%s\": invalid fractional seconds '%s'; can use at most 9 digits",
dateStr, m.group(1).substring(1)
), start);
}
// fall through
case 3:
msecs += (dateStr.charAt(start+2) - '0');
case 2:
msecs += 10 * (dateStr.charAt(start+1) - '0');
case 1:
msecs += 100 * (dateStr.charAt(start) - '0');
break;
case 0:
break;
}
cal.set(Calendar.MILLISECOND, msecs);
}
return cal.getTime();
}
formatStr = DATE_FORMAT_STR_ISO8601;
}
throw new ParseException
(String.format("Cannot parse date \"%s\": while it seems to fit format '%s', parsing fails (leniency? %s)",
dateStr, formatStr, _lenient),
// [databind#1742]: Might be able to give actual location, some day, but for now
// we can't give anything more indicative
0);
}
private static int _parse4D(String str, int index) {
return (1000 * (str.charAt(index) - '0'))
+ (100 * (str.charAt(index+1) - '0'))
+ (10 * (str.charAt(index+2) - '0'))
+ (str.charAt(index+3) - '0');
}
private static int _parse2D(String str, int index) {
return (10 * (str.charAt(index) - '0'))
+ (str.charAt(index+1) - '0');
}
protected Date parseAsRFC1123(String dateStr, ParsePosition pos)
{
if (_formatRFC1123 == null) {
_formatRFC1123 = _cloneFormat(DATE_FORMAT_RFC1123, DATE_FORMAT_STR_RFC1123,
_timezone, _locale, _lenient);
}
return _formatRFC1123.parse(dateStr, pos);
}
/*
/**********************************************************
/* Helper methods, other
/**********************************************************
*/
private final static DateFormat _cloneFormat(DateFormat df, String format,
TimeZone tz, Locale loc, Boolean lenient)
{
if (!loc.equals(DEFAULT_LOCALE)) {
df = new SimpleDateFormat(format, loc);
df.setTimeZone((tz == null) ? DEFAULT_TIMEZONE : tz);
} else {
df = (DateFormat) df.clone();
if (tz != null) {
df.setTimeZone(tz);
}
}
if (lenient != null) {
df.setLenient(lenient.booleanValue());
}
return df;
}
protected void _clearFormats() {
_formatRFC1123 = null;
}
protected Calendar _getCalendar(TimeZone tz) {
Calendar cal = _calendar;
if (cal == null ) {
_calendar = cal = (Calendar)CALENDAR.clone();
}
if (!cal.getTimeZone().equals(tz) ) {
cal.setTimeZone(tz);
}
cal.setLenient(isLenient());
return cal;
}
protected static <T> boolean _equals(T value1, T value2) {
if (value1 == value2) {
return true;
}
return (value1 != null) && value1.equals(value2);
}
}