端端舝

斑硃措硃8井日17尺
2022-09-16 菴98隙扦囀辭�頗
onozaty

反元戶卞
? Java8(LTS)毛妏中適仃化中化﹜公欠公欠Java17(LTS)卞五曰井尹方丹
井午佷勻化中月�砃仃卞﹜灍蕣卞妏中公丹卅辻夔毛畿賡
? 逃桶氪赻旯反﹜引分Java8匹戊奈玉𤩸中化中月仇午互嗣中?

伊戊奈玉 (Java16)
? 奶立亙奈正皮伙(祥劐卅)犯奈正毛悵厥允月弁仿旦毛��g卞隅膽匹五
月方丹卞卅勻凶
? 白奴奈伙玉及伉旦玄毛�徭允月分仃匹﹜狟�互赻�腔卞隅膽今木月
? 戊件旦玄仿弁正
? 跪白奴奈伙玉及失弁本扔
? equals
? hashCode
? toString
? 伊戊奈玉?弁仿旦 - Java晟惤載陔 - Oracle Help Center
https://github.com/onozaty/redmine-view-customize
統蕉

? class及測歹曰卞record匹隅膽仄﹜靡ゴ及摽卞白奴奈伙玉及伉旦玄毛
�徭
? 狟�及㻢𨃨弁仿旦午肮脹卞卅月
public final class Rectangle {
private final int length;
private final int width;
public Rectangle(int length, int width) {
this.length = length;
this.width = width;
}
public int length() { return this.length; }
public int width() { return this.width; }
public boolean equals(Object obj) {...} // 吽謹(跪白奴奈伙玉毛妏勻凶羥ピ卅�I燴)
public int hashCode() {...} // 吽謹(跪白奴奈伙玉毛妏勻凶羥ピ卅�I燴)
public String toString() {...} // 吽謹(跪白奴奈伙玉毛妏勻凶羥ピ卅�I燴)
}
public record Rectangle(int length, int width) { }

// 白奴奈伙玉毛硌隅仄化汜傖
Rectangle rectangle = new Rectangle(1, 2);
// get皿伉白奴永弁旦反葆井卅中
assertThat(rectangle.length())
.isEqualTo(1);
assertThat(rectangle.width())
.isEqualTo(2);
// 弁仿旦靡ㄚ白奴奈伙玉匹囀⺍毛桶允
assertThat(rectangle.toString())
.isEqualTo("Rectangle[length=1, width=2]");
Rectangle other = new Rectangle(1, 2);
// 白奴奈伙玉及�毛妏勻化肮珨俶互民尼永弁今木月
assertThat(rectangle.hashCode())
.isEqualTo(other.hashCode());
assertThat(rectangle.equals(other))
.isTrue();
assertThat(rectangle.area()).isEqualTo(2);

? 黃赻丟末永玉手哫晟匹五月
? 戊件旦玄仿弁正卞民尼永弁�I燴毛袚樓仄凶曰﹜黃赻戊件旦玄仿弁正
毛袚樓匹五月
public record Rectangle(int length, int width) {
public Rectangle {
if (length < 0 || width < 0) {
throw new IllegalArgumentException();
}
}
public Rectangle(int length) {
this(length, 0);
}
}
public record Rectangle(int length, int width) {
public int area() {
return length * width;
}
}

? 伊戊奈玉互丐木壬Lombok毛秏六月午中丹歹仃匹手卅中
? 伊戊奈玉反奶立亙奈正皮伙卅手及仄井隅膽匹五卅中
? 白奴奈伙玉杅互嗣仁卅月午Builder互剠中午仄氏升中
? 剠燴卞离五𡥼尹內卞﹜白奴奈伙玉互屾卅中手及匹妏勻化中仁及互方
今公丹
? 正皿伙腔卅手及午井

氾平旦玄皮伕永弁 (Java15)
? 恚杅俴卞引凶互月恅趼蹈毛哫晟匹五月方丹卞卅勻凶
? 丟斥乓奈卅皿伕弘仿立件弘晟惤匹𤩸仃卅井勻凶及反Java仁日中匹反
? Programmer's Guide to Text Blocks - Oracle Help Center
https://docs.oracle.com/javase/jp/15/text-blocks/index.html
統蕉

? ※§§ 匹�氏匹𤩸仁
? ※§§ 及摽卞蜊俴匹棒及俴井日互恅趼蹈及嶱宎
? 氾平旦玄皮伕永弁囀及蜊俴反?n卞卅月
? 奶件犯件玄反珨楓シ中弇离互價𨃨卞卅月
String text = """
1俴醴
2俴醴
""";
assertThat(text)
.isEqualTo("1俴醴?n2俴醴?n");
String text = """
1俴醴
2俴醴(奶件犯件玄)
""";
assertThat(text)
.isEqualTo("1俴醴?n 2俴醴(奶件犯件玄)?n");

? 藺帣及旦矢奈旦反赻�腔卞壺�今木月
? 旦矢奈旦毛葆迵仄凶中�磁卞反 ?s 毛瞳蚚
藺帣卞葆迵允木壬﹜公木方曰ゴ及旦矢奈旦手漪戶化鋤厥今木月
? 蜊俴毛葆迵仄凶仁卅中�磁卞反﹜藺帣卞 ? 毛葆迵
String text = """
1俴醴 ?s
2俴醴?s
""";
assertThat(text)
.isEqualTo("1俴醴 ?n2俴醴 ?n");
String text = """
1俴醴?
2俴醴?
""";
assertThat(text)
.isEqualTo("1俴醴2俴醴");

? SQL毛戊奈玉卞鎚戶煋戈方丹卅�磁支﹜氾旦玄戊奈玉匹及掀廌卅升
匹笭惘仄公丹
? MyBatis匹SQL毛失用氾奈扑亦件匹𤩸中化中月互﹜恚杅俴恅趼蹈互𤩸仃卅中
互凶戶卞踏引匹反Groovy匹𤩸中化中凶
@Select("""
SELECT
*
FROM
customers
WHERE
id = #{id}
""")
public Customer findOne(@Param("id") int id);

釦喧娶勳紳眶弁仿旦憝蟀

String#formatted (Java15) ↗氾平旦玄皮伕永弁憝窣匹袚樓
? 踏引匹String.format匹網太堤仄化中凶手及毛﹜String及奶件旦正件
旦丟末永玉午仄化網太堤六月方丹卞仄凶手及午仄化formatted丟
末永玉互袚樓
String formatText = "%,d�匹允﹝";
String text = formatText.formatted(1234);
assertThat(text).isEqualTo("1,234�匹允﹝");
// String.format匹肮脹及戊奈玉
String text = String.format(formatText, 1234);

String#formatted (Java15) ↗氾平旦玄皮伕永弁憝窣匹袚樓
? 氾平旦玄皮伕永弁卞劐杅鎚戶煋心反⻌日卅井勻凶互﹜formatted丟
末永玉毛妏丹仇午匹﹜(嗣屾)歹井曰支允仁𤩸仁仇午互匹五月
? 劐杅鎚戶煋心腔卅手及反﹜�e及辻夔蜊囡午仄化𨈘�
? JEP draft: String Templates (Preview) https://openjdk.org/jeps/8273943
String text = """
%s今氏﹝
踢謞反%,d�匹允﹝
""".formatted("怮檔", 1234);
assertThat(text).isEqualTo("怮檔今氏﹝?n踢謞反1,234�匹允﹝?n");

String#stripIndent (Java15) ↗氾平旦玄皮伕永弁憝窣匹袚樓
? stripIndent反﹜恚杅俴及恅趼蹈井日珨楓シ中奶件犯件玄煦及諾啞毛
龰曰壺仁
String text = " 1?n 2?n 3";
assertThat(text.stripIndent()).isEqualTo("1?n 2?n 3"); // 珂螹俴卞丐歹六化奶件犯件玄互1勾龰曰壺井木凶

String#translateEscapes (Java15)
? translateEscapes反﹜巨旦弗奈皿扑奈弗件旦毛劐𡥼
? 凶午尹壬﹜?n午中丹2恅趼毛蜊俴戊奈玉(U+000A)卞劐𡥼仄化仁月
? ⻌薯�午仄化旦弗奈皿扑奈弗件旦毛衄�卞仄凶中�磁卞妏尹公丹分
互﹜Unicode巨旦弗奈皿(?u0020午井)卞反�𡛟仄化中卅中及匹蛁砩
? https://docs.oracle.com/javase/jp/17/docs/api/java.base/java/lang/String.ht
ml#translateEscapes()
String text = "a??n??tb";
System.out.println(text); // a?n?tb
assertThat(text.translateEscapes()).isEqualTo("a?n?tb");
System.out.println(text.translateEscapes()); // a
// b

String#repeat (Java11)
? String#repeat 匹�砓恅趼蹈毛硌隅隙杅靜曰殿仄凶恅趼蹈毛釬傖匹五
String text = "a".repeat(10);
assertThat(text).isEqualTo("aaaaaaaaaa");

String#strip﹜stripLeading﹜stripTrailing (Java11)
? String#trim﹜trimLeft﹜trimRight 午肮元方丹卅手及分互﹜�褒旦
矢奈旦卅升手�砓卞卅月午仇欠互�卅月
? trim分午ASCII匹0x20眕狟互�砓
(旦矢奈旦﹜正皮﹜蜊俴﹜公及坻秶郘戊奈玉)
? strip分午奻�卞皿仿旦仄化Unicode及市氾打伉匹諾啞恅趼午卅月方丹卅手及
卅升手�砓
(�褒旦矢奈旦支僇邈Еピ曰恅趼(PARAGRAPH SEPARATOR)午井)
String text = "?n?u3000 a ?u3000?n";
assertThat(text.strip()).isEqualTo("a");
assertThat(text.stripLeading()).isEqualTo("a ?u3000?n");
assertThat(text.stripTrailing()).isEqualTo("?n?u3000 a");
// trim炵分午�褒旦矢奈旦反秏尹卅中
assertThat(text.trim()).isEqualTo("?u3000 a ?u3000");

String#isBlank (Java11)
? String#isBlank 匹諾啞井升丹井瓚隅匹五月方丹卞
assertThat(" ".isBlank()).isTrue();
assertThat("?n?t?u3000".isBlank()).isTrue();

String#lines (Java11)
? String#lines 匹俴仍午及恅趼蹈及Stream毛龰腕匹五月方丹卞卅勻凶
? 眕ゴ井日 Files.lines 匹白央奶伙井日掂心煋心媆反肮元仇午互匹五化中凶
String text = "a?nb?r?nc";
Stream<String> lines = text.lines();
assertThat(lines.count()).isEqualTo(3);

String#indent (Java12)
? String 及 indent 丟末永玉匹﹜硌隅仄凶恅趼杅煦及奶件犯件玄毛葆仃
日木月方丹卞卅勻凶
String base = "1?n2?n?n";
String indented = base.indent(2);
assertThat(indented).isEqualTo(" 1?n 2?n ?n");

String#transform (Java12)
? String 毛竘杅卞龰月丟末永玉毛灍俴仄化磐彆毛殿允丟末永玉午仄化﹜
transform 丟末永玉互袚樓
? 丟末永玉網太堤仄1隙分午﹜丐引曰丟伉永玄毛覜元卅中互﹜丟末永
玉網太堤仄互適仁方丹卅�磁卞反﹜�I燴互酘井日衵卞霜木月方丹卞
𤩸仃月及匹﹜掂心支允仁卅月
int num = "1".transform(Integer::parseInt);
// 仇木午肮元
int num = Integer.parseInt("1");
int num = "12#34".transform(this::clean).transform(Integer::valueOf);

莽滄勳喧釵堯宒 (Java14)
? switch毛宒午仄化手𤩸仃月方丹卞卅勻凶
? 宒卅及匹switch互�毛殿允方丹卞
? 宒 - Java晟惤載陔 - Oracle Help Center
https://docs.oracle.com/javase/jp/13/language/switch-expressions.html
統蕉

? switch恅匹沭璃卞𡛟元化�毛偞隅允月方丹卅手及互﹜莽滄勳喧釵堯宒卞离
五𡥼尹日木月
// switch恅
int numLetters;
switch (day) {
case MONDAY:
case FRIDAY:
case SUNDAY:
numLetters = 6;
break;
case TUESDAY:
numLetters = 7;
break;
case THURSDAY:
case SATURDAY:
numLetters = 8;
break;
case WEDNESDAY:
numLetters = 9;
break;
default:
throw new IllegalStateException();
}
// 莽滄勳喧釵堯宒
int numLetters = switch (day) {
case MONDAY, FRIDAY, SUNDAY -> 6;
case TUESDAY -> 7;
case THURSDAY, SATURDAY -> 8;
case WEDNESDAY -> 9;
default -> throw new IllegalStateException();
};

? 陔凶卞袚樓今木凶失伕奈case仿矛伙(失伕奈�恅)井﹜踏引匹籵曰及
戊伕件case仿矛伙ㄚyield匹�毛殿允
// 失伕奈case仿矛伙
case MONDAY, FRIDAY, SUNDAY -> 6;
case TUESDAY -> 7;
case THURSDAY, SATURDAY -> 8;
case WEDNESDAY -> 9;
};
// 戊伕件case仿矛伙ㄚyield
case MONDAY:
case FRIDAY:
case SUNDAY:
yield 6;
case TUESDAY:
yield 7;
case THURSDAY:
case SATURDAY:
yield 8;
case WEDNESDAY:
yield 9;
default:
};

? 失伕奈case仿矛伙匹手﹜恚杅及宒互斛猁卅�磁反﹜皮伕永弁ㄚyield
毛妏丹
case MONDAY, FRIDAY, SUNDAY -> {
System.out.println(6);
yield 6;
}
case TUESDAY -> {
yield 7;
}
case THURSDAY, SATURDAY -> {
yield 8;
}
case WEDNESDAY -> {
yield 9;
}
};

? 戊伕件case仿矛伙匹手﹜仿矛伙毛市件穴Еピ曰匹恚杅𤩸仃月方丹卞
卅勻凶
? 暫湔及switch恅匹手𤩸仃月
switch (day) {
case MONDAY, FRIDAY, SUNDAY:
break;
case TUESDAY:
break;
case THURSDAY, SATURDAY:
break;
case WEDNESDAY:
break;
default:
}

? 失伕奈case仿矛伙午戊伕件case仿矛伙及2勾及𤩸五源互丐月互﹜失
伕奈case仿矛伙分午break咭木化砩�六內白巧奈伙旦伙奈允月仇午
互剠中及匹﹜失伕奈case仿矛伙及源互方今公丹
? 失伕奈case仿矛伙匹皮伕永弁匹𤩸中凶�磁匹手﹜yield互剠中午巨仿奈卞卅
月

由正奈件穴永民件弘勳紳莽喧硃紳釵梗棗款

由正奈件穴永民件弘勳紳莽喧硃紳釵梗棗款 (Java16)
? instanceof 匹倰民尼永弁允月及午肮媆卞﹜公及倰及劐杅毛隅膽匹五
Object value = 10;
if (value instanceof Integer num) {
assertThat(num).isEqualTo(10);
}
// 眕ゴ分午婬僅平乓旦玄允月斛猁互丐勻凶
if (value instanceof Integer) {
Integer num = (Integer) value;
assertThat(num).isEqualTo(10);
}

伕奈市伙劐杅及倰芢蹦

伕奈市伙劐杅及倰芢蹦(var) (Java10)
? var午中丹�恅互袚樓今木﹜伕奈市伙劐杅及�磁卞反var匹倰互吽謹
匹五月方丹卞卅勻凶
var num = 1;
var list = List.of("a");
// 奻�反狟�午肮元
int num = 1;
List<String> list = List.of("a");

伕奈市伙劐杅及倰芢蹦(var) (Java10)
? 衵煘匹倰互赻隴卅手及反謎中互﹜丟末永玉及𥽋曰及測⻌卅升反倰互
歹井曰內日仁卅月及匹蛁砩
? IDE匹允什卞倰互歹井月午反中尹﹜戊奈玉心凶分仃匹倰互歹井勻凶源互謎中
及匹﹜歹井曰勿日仁卅月方丹卅由正奈件毛旌仃月凶戶卞丐引曰妏歹卅公丹
// 倰互赻隴(衵煘匹歹井月)
var calculator = new Calculator();
var list = List.of("a");
// 倰互歹井曰內日仁卅月
var result = compute();

奶件正白尼奈旦卞云仃月梯娶勳措硃喧梗丟末永玉及扔禾奈玄

奶件正白尼奈旦卞云仃月梯娶勳措硃喧梗丟末永玉及扔禾奈玄 (Java9)
? 奶件正奈白尼奈旦匹private丟末永玉互隅膽匹五月方丹卞卅勻凶
? private卅及匹灍蚾弁仿旦井日反統桽匹五卅中
? 奶件正奈白尼奈旦及犯白巧伙玄丟末永玉支static丟末永玉井日及統桽
public interface Hoge {
private void fuga() {
}
}

戊伊弁扑亦件及白央弁玄伉丟末永玉 (Java9)
? 戊伊弁扑亦件弁仿旦(List﹜Set﹜Map)及白央弁玄伉丟末永玉互袚樓
今木凶
? �化奶立亙奈正皮伙(袚樓/祅壺/劐載祥褫)卅戊伊弁扑亦件卞卅月
// List
List<String> list = List.of("a", "b", "c");
// Set
Set<String> set = Set.of("a", "b", "c");
// Map
Map<Integer, String> map1 = Map.of(1, "a", 2, "b", 3, "c");
// Map#ofEntries 毛妏勻凶源互﹜平奈午�及本永玄互歹井曰支允中
Map<Integer, String> map2 = Map.ofEntries(Map.entry(1, "a"), Map.entry(2, "b"), Map.entry(3, "c"));

戊伊弁扑亦件及劐載祥褫卅戊疋奈釬傖 (Java10)
? List﹜Set﹜Map 卞 copyOf 午中丹static丟末永玉互袚樓今木﹜劐載祥
褫卅恚庨互汜傖匹五月方丹卞卅勻凶
? 戊疋奈啋互劐載祥褫卅�磁﹜恚庨毛釬月斛猁互卅中及匹﹜戊疋奈啋
及奶件旦正件旦赻极互殿�今木月
var base = List.of("a", "b", "c");
// base反劐載祥褫卅及匹﹜base赻极互殿今木月
var copied = List.copyOf(base);
assertThat(copied == base).isTrue();
var base = Arrays.asList("a", "b", "c");
// base反劐載褫夔卅及匹﹜劐載祥褫午仄凶恚庨互殿今木月
var copied = List.copyOf(base);
assertThat(copied == base).isFalse();

Collection#toArray(IntFunction<T[]> generator) (Java11)
? Collection#toArray 匹竘杅卞饜蹈毛new允月憝杅毛硌隅匹五月方丹卞
卅勻凶
? 眕ゴ反饜蹈毛汜傖仄化傾仄化中凶(new String[0]午井)及互﹜戊件旦
玄仿弁正毛丟末永玉統桽匹硌隅匹五月方丹卞卅勻凶覜元
List<String> list = List.of("a", "b", "c");
String[] array = list.toArray(String[]::new);
// 眕ゴ反饜蹈赻极毛傾仄化中凶
String[] array = list.toArray(new String[list.size()]);

Path.of (Java11)
? Paths.get 分勻凶及互﹜Path.of 匹𤩸仃月方丹卞卅勻凶
? 坻及釬楊午磁歹六凶方丹卅覜元
Path path1 = Paths.get("dir");
Path path2 = Path.of("dir");
assertThat(path2).isEqualTo(path1);

Files.writeString﹜readString (Java11)
? Files.writeString 互袚樓今木﹜1丟末永玉匹恅趼及𤩸五煋心互俴尹月
方丹卞卅勻凶
? 踏引匹手 Files.write 匹田奶玄饜蹈反𤩸五煋戶凶互﹜公木毛String及引引硌隅
匹五月方丹卞卅勻凶覜元
? 肮�卞 readString 匹1丟末永玉匹掂心煋心互俴尹月方丹卞卅勻凶
? 仇切日手踏引匹反 Files.readAllBytes 匹田奶玄饜蹈反掂心煋戶凶
Files.writeString(filePath, "丐中丹尹云", StandardCharsets.UTF_8);
String text = Files.readString(filePath, StandardCharsets.UTF_8);
assertThat(text).isEqualTo("丐中丹尹云");

InputStream#readAllBytes﹜transferTo (Java9)
? InputStream 卞�化及囀⺍毛掂心煋戈 readAllBytes 互袚樓今木凶
? 白央奶伙及�磁卞反﹜Files.readAllBytes 互丐月互﹜公木午肮元仇午互
InputStream 卞�仄化手堤懂月方丹卞卅勻凶
? 囀⺍毛 OutputStream 卞𤩸五煋戈 transferTo 手袚樓今木凶
byte[] results = inputStream.readAllBytes();
inputStream.transferTo(outputStream);

Stream#toList (Java16)
? Stream卞toList丟末永玉互袚樓
? collect(Collectos.toList())匹𤩸中化中凶預垀互﹜允勻五曰午仄凶倛匹
𤩸仃月方丹卞
List<String> list = Stream.of("a", "b").toList();
// 踏引匹
List<String> list = Stream.of("a", "b").collect(Collectors.toList());

Stream#toList (Java16)
? Stream及toList反祥劐卅伉旦玄毛殿允
? 袚樓/祅壺/劐載毛俴丹午﹜UnsuptorpedOperationException互逃汜
? Collectors.toList匹殿允伉旦玄反﹜API帊�午仄化反褫劐俶反悵偩今
木化中卅中互﹜政婓及灍蚾午仄化反ArrayList卞卅勻化中月凶戶﹜袚
樓/祅壺/劐載反堤懂化仄引丹袨颷
? collect(Collectors.toList())毛toList()卞离五𡥼尹月午﹜袚樓/祅壺/劐載互匹五
卅仁卅曰﹜�觳互堤月褫夔俶手丐月及匹蛁砩互斛猁
? Java10匹Collectors.toUnmodifiableList手袚樓今木化中月
List<String> list = Stream.of("a", "b").toList();
list.set(0, "x"); // UnsupportedOperationException 互逃汜
Stream.of("a", "b").toList(); // 祥劐
Stream.of("a", "b").collect(Collectors.toList()); // API帊�午仄化反褫劐俶反悵偩今木卅中午卅勻化中月互﹜政婓及灍蚾午仄化反褫劐
Stream.of("a", "b").collect(Collectors.toUnmodifiableList()); // 祥劐

Stream#mapMulti (Java16)
? flatMap午侔凶方丹卅丟末永玉午仄化mapMulti互袚樓
? flatMap互Stream毛殿允及卞�仄化﹜mapMulti反傾今木凶Consumer
卞�仄化�毛偞隅仄化中仁倛午卅月
List<String> upperChars =
Stream.of("abc", "xyz")
.mapMulti((String str, Consumer<String> consumer) -> {
for (char c : str.toCharArray()) {
consumer.accept(String.valueOf(c).toUpperCase());
}
})
.toList();
assertThat(upperChars)
.containsExactly("A", "B", "C", "X", "Y", "Z");
// flatMap匹𤩸中凶�磁
List<String> upperChars =
Stream.of("abc", "xyz")
.flatMap(str -> str.chars()
.mapToObj(c -> String.valueOf((char) c).toUpperCase()))
.toList();

Stream#takeWhile﹜dropWhile (Java9)
? takeWhile匹硌隅仄凶沭璃毛㦤凶允嶲及犯奈正毛�砓卞
? dropWhile匹硌隅仄凶沭璃毛㦤凶允嶲及犯奈正毛�砓俋卞
// 2及�\杅匹100眕狟及手及毛А戶月
int[] results = IntStream.iterate(2, x -> x * 2)
.takeWhile(x -> x <= 100)
.toArray();
assertThat(results)
.containsExactly(2, 4, 8, 16, 32, 64);
// 2及�\杅匹100眕奻﹜1000眕狟及手及毛А戶月
int[] results = IntStream.iterate(2, x -> x * 2)
.dropWhile(x -> x < 100)
.toArray();
assertThat(results)
.containsExactly(128, 256, 512);

Stream#takeWhile﹜dropWhile (Java9)
? filter午及綃中午仄化﹜takeWhile反沭璃卞珨祡仄卅仁卅勻凶日
Stream�I燴赻极毛砦戶月
? 猁匼互剠秶癹卅Stream支﹜湮五卅Stream及珂螹及珨窒仄井妏歹卅中方丹卅
�磁卞衄蚚
? filter分午�化及猁匼卞�仄化�I燴毛俴丹仇午卞卅月
// takeWhile分午﹜剠秶癹卅Stream匹手沭璃卞珨祡仄卅仁卅勻凶媆萸匹砦戶化仁木月
IntStream.iterate(2, x -> x * 2)
.toArray();
// filter分午﹜沭璃卞珨祡仄卅仁化手Stream�I燴反輥適今木月ˊ皺歹日卅中
IntStream.iterate(2, x -> x * 2)
.filter(x -> x <= 100)
.toArray();

Stream.ofNullable (Java9)
? ofNullable 反﹜null及�磁反諾及Stream毛﹜null眕俋及�磁反硌隅今
木凶�毛厥勾猁匼杅1及Stream毛殿允
long count = Stream.ofNullable("a").count();
assertThat(count).isEqualTo(1);
long count = Stream.ofNullable(null).count();

Predicate.not (Java11)
? Predicate.not 匹 Predicate 毛毀�今六日木月方丹卞卅勻凶
? 毀�及凶戶卞丟末永玉統桽毛淓戶化中凶方丹卅�垀匹丟末永玉統桽
互妏尹月方丹卞卅月
long notEmptyCount = Stream.of("", "x", "", "x", "x")
.filter(Predicate.not(String::isEmpty))
.count();
assertThat(notEmptyCount).isEqualTo(3);
// 眕ゴ反毀�今六凶中午五反仿丞母匹
long notEmptyCount = Stream.of("", "x", "", "x", "x")
.filter(x -> !x.isEmpty())
.count();

倏梯喧勳棗紳硃梭憝蟀

Optional#ifPresentOrElse (Java9)
? ifPresent 反�互丐勻凶午五及心灍俴今木月互﹜�互剠井勻凶媆及失
弁扑亦件手肮媆卞灍俴匹五月 ifPresentOrElse 互袚樓今木凶
AtomicInteger hasValueCounter = new AtomicInteger();
AtomicInteger emptyValueCounter = new AtomicInteger();
Optional<String> value = Optional.ofNullable(null);
value.ifPresentOrElse(
v -> hasValueCounter.incrementAndGet(),
() -> emptyValueCounter.incrementAndGet());
assertThat(hasValueCounter.get()).isEqualTo(0);
assertThat(emptyValueCounter.get()).isEqualTo(1);

Optional#or (Java9)
? orElse 午侔凶方丹卅手及午仄化﹜or 互袚樓今木凶
? or 反 Optional 毛殿允 Supplier 毛硌隅
? Optional 及引引犯白巧伙玄�匹娗俇允月方丹卅午五卞妏尹公丹
Optional<String> value = Optional.empty();
Optional<String> result = value.or(() -> Optional.of(""));
assertThat(result.get()).isEqualTo("");
// 龰曰堤允蕣卞鎚戶月方丹卅�磁卞反﹜orElse匹手坋煦
assertThat(value.orElse("")).isEqualTo("");

Optional#stream (Java9)
? stream 丟末永玉匹 Stream 卞劐𡥼匹五月方丹卞卅勻凶
? �互丐月�磁反�互珨勾跡慮今木凶 Stream ﹜�互剠中�磁反諾及
Stream 卞卅月
Optional<String> value = Optional.of("a");
long count = value.stream().count();
Optional<String> value = Optional.empty();
long count = value.stream().count();

Optional#isEmpty (Java11)
? Optional 卞 isEmpty 互袚樓
? isPresent 及欄
Optional<String> value = Optional.ofNullable(null);
assertThat(value.isEmpty()).isTrue();
assertThat(value.isPresent()).isFalse();

云歹曰卞
? 伉伉奈旦扔奶弁伙互劐歹曰﹜陔仄中辻夔互圉爛卞1隙⻌月方丹卞
卅勻凶仇午匹﹜Java手升氏升氏𤩸五支允仁卅勻化中月
? 1.4井日8仁日中引匹反﹜伉伉奈旦嶲路手杅爛午墿仁化﹜礿笴仄化中月覜元
互仄凶
? 辻夔午田奈斥亦件毛憂勿仃化伉伉奈旦正奶立件弘毛蕉尹月及匹反卅仁﹜伉
伉奈旦笚ヽ毛𢜪戶化﹜公及正奶立件弘匹堤六月辻夔毛堤允午中勻凶倛卞
卅勻凶仇午匹﹜婌戶卞Preview午仄化伉伉奈旦仄﹜白奴奈玉田永弁毛腕木月
方丹卞卅勻凶及反﹜Java及筳趙及旦疋奈玉毛厒戶凶及匹反
? 踏摽手方今公丹卅辻夔互軑隅今木化中月及匹﹜引凶棒及LTS互伉
伉奈旦今木凶正奶立件弘匹�仄化心化﹜逃桶仄凶中

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