{"id":12559,"date":"2023-09-05T15:19:34","date_gmt":"2023-09-05T07:19:34","guid":{"rendered":"https:\/\/92it.top\/?p=12559"},"modified":"2023-09-05T15:19:34","modified_gmt":"2023-09-05T07:19:34","slug":"java8%e4%b8%ad%e6%96%b0%e5%88%a4%e7%a9%ba%e6%96%b9%e6%b3%95%e4%b9%8boptional%e7%b1%bb%e7%9a%84%e4%bd%bf%e7%94%a8%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/92it.top\/?p=12559","title":{"rendered":"Java8\u4e2d\u65b0\u5224\u7a7a\u65b9\u6cd5\u4e4bOptional\u7c7b\u7684\u4f7f\u7528\u8be6\u89e3"},"content":{"rendered":"\n

\u8ba4\u8bc6Optional<\/strong><\/p>\n\n\n\n

\n\n\n\n

Opitonal\u7c7b\u5c31\u662fJava\u63d0\u4f9b\u7684\u4e3a\u4e86\u89e3\u51b3\u5927\u5bb6\u5e73\u65f6\u5224\u65ad\u5bf9\u8c61\u662f\u5426\u4e3a\u7a7a\u7528\uff0c\u901a\u5e38\u4f1a\u7528 null!=obj<\/code> \u8fd9\u6837\u7684\u65b9\u5f0f\u5b58\u5728\u7684\u5224\u65ad\uff0c\u4ece\u800c\u4ee4\u4eba\u5934\u75bc\u5bfc\u81f4\u7a7a\u6307\u9488\u5f02\u5e38\uff0c\u540cOptional\u7684\u5b58\u5728\u53ef\u4ee5\u8ba9\u4ee3\u7801\u66f4\u52a0\u7b80\u5355\uff0c\u53ef\u8bfb\u6027\u8ddf\u9ad8\uff0c\u4ee3\u7801\u5199\u8d77\u6765\u66f4\u9ad8\u6548<\/p>\n\n\n\n

Student student = new Student();\nif (null == student){\n    return \"student\u4e3anull\";\n}\nreturn student;\n<\/pre>\n\n\n\n
Student student = new Student();\nreturn Optional.ofNullable(student).orElse(\"student\u4e3anull\");\n<\/pre>\n\n\n\n
\u6d4b\u8bd5\u5c55\u793a\u7c7bStudent \u4ee3\u7801(\u5982\u679c\u6709\u670b\u53cb\u4e0d\u660e\u767d\u53ef\u4ee5\u770b\u4e00\u4e0b\u8fd9\u4e2a)\uff1a<\/p>\n\n\n\n
@Data\n@AllArgsConstructor\n@NoArgsConstructor\npublic class Student {\n    private String name;\n    private Integer age;\n}<\/pre>\n\n\n\n
Optional\u5bf9\u8c61\u521b\u5efa<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u9996\u5148\u6211\u4eec\u5148\u6253\u5f00Optional\u7684\u5185\u90e8,\u53bb\u4e00\u63a2\u7a76\u7adf \u5148\u628a\u51e0\u4e2a\u521b\u5efaOptional\u5bf9\u8c61\u7684\u65b9\u6cd5\u63d0\u53d6\u51fa\u6765<\/p>\n\n\n\n
public final class Optional<T> {\n   private static final Optional<?> EMPTY = new Optional<>();\n   private final T value;\n   \/\/ \u6211\u4eec\u53ef\u4ee5\u770b\u5230\u4e24\u4e2a\u6784\u9020\u65b9\u683c\u90fd\u662fprivate \u79c1\u6709\u7684\n   \/\/ \u8bf4\u660e \u6211\u4eec\u6ca1\u529e\u6cd5\u5728\u5916\u9762\u53bbnew\u51fa\u6765Optional\u5bf9\u8c61\n   private Optional() {\n        this.value = null;\n    }\n   private Optional(T value) {\n        this.value = Objects.requireNonNull(value);\n    }\n    \/\/ \u8fd9\u4e2a\u9759\u6001\u65b9\u6cd5\u5927\u81f4 \u662f\u521b\u5efa\u51fa\u4e00\u4e2a\u5305\u88c5\u503c\u4e3a\u7a7a\u7684\u4e00\u4e2a\u5bf9\u8c61\u56e0\u4e3a\u6ca1\u6709\u4efb\u4f55\u53c2\u6570\u8d4b\u503c\n   public static<T> Optional<T> empty() {\n        @SuppressWarnings(\"unchecked\")\n        Optional<T> t = (Optional<T>) EMPTY;\n        return t;\n    }\n    \/\/ \u8fd9\u4e2a\u9759\u6001\u65b9\u6cd5\u5927\u81f4 \u662f\u521b\u5efa\u51fa\u4e00\u4e2a\u5305\u88c5\u503c\u975e\u7a7a\u7684\u4e00\u4e2a\u5bf9\u8c61 \u56e0\u4e3a\u505a\u4e86\u8d4b\u503c\n   public static <T> Optional<T> of(T value) {\n        return new Optional<>(value);\n    }\n    \/\/ \u8fd9\u4e2a\u9759\u6001\u65b9\u6cd5\u5927\u81f4\u662f \u5982\u679c\u53c2\u6570value\u4e3a\u7a7a\uff0c\u5219\u521b\u5efa\u7a7a\u5bf9\u8c61\uff0c\u5982\u679c\u4e0d\u4e3a\u7a7a\uff0c\u5219\u521b\u5efa\u6709\u53c2\u5bf9\u8c61\n   public static <T> Optional<T> ofNullable(T value) {\n        return value == null ? empty() : of(value);\n    }\n }<\/pre>\n\n\n\n
\u518d\u505a\u4e00\u4e2a\u7b80\u5355\u7684\u5b9e\u4f8b\u5c55\u793a \u4e0e\u4e0a\u9762\u5bf9\u5e94<\/p>\n\n\n\n
\/\/ 1\u3001\u521b\u5efa\u4e00\u4e2a\u5305\u88c5\u5bf9\u8c61\u503c\u4e3a\u7a7a\u7684Optional\u5bf9\u8c61\nOptional<String> optEmpty = Optional.empty();\n\/\/ 2\u3001\u521b\u5efa\u5305\u88c5\u5bf9\u8c61\u503c\u975e\u7a7a\u7684Optional\u5bf9\u8c61\nOptional<String> optOf = Optional.of(\"optional\");\n\/\/ 3\u3001\u521b\u5efa\u5305\u88c5\u5bf9\u8c61\u503c\u5141\u8bb8\u4e3a\u7a7a\u4e5f\u53ef\u4ee5\u4e0d\u4e3a\u7a7a\u7684Optional\u5bf9\u8c61\nOptional<String> optOfNullable1 = Optional.ofNullable(null);\nOptional<String> optOfNullable2 = Optional.ofNullable(\"optional\");<\/pre>\n\n\n\n
Optional.get()\u65b9\u6cd5(\u8fd4\u56de\u5bf9\u8c61\u7684\u503c)<\/strong><\/p>\n\n\n\n
\n\n\n\n
get()\u65b9\u6cd5\u662f\u8fd4\u56de\u4e00\u4e2aoption\u7684\u5b9e\u4f8b\u503c<\/p>\n\n\n\n
\u6e90\u7801\uff1a<\/p>\n\n\n\n
public T get() {\n    if (value == null) {\n        throw new NoSuchElementException(\"No value present\");\n    }\n    return value;\n}<\/pre>\n\n\n\n
\u4e5f\u5c31\u662f\u5982\u679cvalue\u4e0d\u4e3a\u7a7a\u5219\u505a\u8fd4\u56de\uff0c\u5982\u679c\u4e3a\u7a7a\u5219\u629b\u51fa\u5f02\u5e38 \u201cNo value present<\/code>\u201d \u7b80\u5355\u5b9e\u4f8b\u5c55\u793a<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nSystem.out.println(Optional.ofNullable(student).get());<\/pre>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
Optional.isPresent()\u65b9\u6cd5(\u5224\u8bfb\u662f\u5426\u4e3a\u7a7a)<\/strong><\/p>\n\n\n\n
\n\n\n\n
isPresent()\u65b9\u6cd5\u5c31\u662f\u4f1a\u8fd4\u56de\u4e00\u4e2aboolean\u7c7b\u578b\u503c\uff0c\u5982\u679c\u5bf9\u8c61\u4e0d\u4e3a\u7a7a\u5219\u4e3a\u771f\uff0c\u5982\u679c\u4e3a\u7a7a\u5219false<\/p>\n\n\n\n
\u6e90\u7801:<\/p>\n\n\n\n
public boolean isPresent() {\n    return value != null;\n}\n\n<\/pre>\n\n\n\n
\u7b80\u5355\u7684\u5b9e\u4f8b\u5c55\u793a:<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nif (Optional.ofNullable(student).isPresent()){\n    System.out.println(\"\u4e0d\u4e3a\u7a7a\");\n}else {\n    System.out.println(\"\u4e3a\u7a7a\");\n}<\/pre>\n\n\n\n
\"\"<\/figure><\/div>\n\n\n\n
Optional.ifPresent()\u65b9\u6cd5(\u5224\u8bfb\u662f\u5426\u4e3a\u7a7a\u5e76\u8fd4\u56de\u51fd\u6570)<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u8fd9\u4e2a\u610f\u601d\u662f\u5982\u679c\u5bf9\u8c61\u975e\u7a7a\uff0c\u5219\u8fd0\u884c\u51fd\u6570\u4f53<\/p>\n\n\n\n
\u6e90\u7801:<\/p>\n\n\n\n
public void ifPresent(Consumer<? super T> consumer) {\n    \/\/\u5982\u679cvalue\u4e0d\u4e3a\u7a7a\uff0c\u5219\u8fd0\u884caccept\u65b9\u6cd5\u4f53\n    if (value != null)\n        consumer.accept(value);\n}<\/pre>\n\n\n\n
\u770b\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nOptional.ofNullable(student).ifPresent(s -> System.out.println(\"\u5e74\u9f84\uff1a\" + s.getAge()));<\/pre>\n\n\n\n
\u5982\u679c\u5bf9\u8c61\u4e0d\u4e3a\u7a7a\uff0c\u5219\u4f1a\u6253\u5370\u8fd9\u4e2a\u5e74\u9f84\uff0c\u56e0\u4e3a\u5185\u90e8\u5df2\u7ecf\u505a\u4e86NPE\uff08\u975e\u7a7a\u5224\u65ad\uff09\uff0c\u6240\u4ee5\u5c31\u4e0d\u7528\u62c5\u5fc3\u7a7a\u6307\u9488\u5f02\u5e38\u4e86<\/p>\n\n\n\n
Optional.filter()\u65b9\u6cd5(\u8fc7\u6ee4\u5bf9\u8c61)<\/strong><\/p>\n\n\n\n
\n\n\n\n
filter()\u65b9\u6cd5\u5927\u81f4\u610f\u601d\u662f\uff0c\u63a5\u53d7\u4e00\u4e2a\u5bf9\u8c61\uff0c\u7136\u540e\u5bf9\u4ed6\u8fdb\u884c\u6761\u4ef6\u8fc7\u6ee4\uff0c\u5982\u679c\u6761\u4ef6\u7b26\u5408\u5219\u8fd4\u56deOptional\u5bf9\u8c61\u672c\u8eab\uff0c\u5982\u679c\u4e0d\u7b26\u5408\u5219\u8fd4\u56de\u7a7aOptional<\/p>\n\n\n\n
\u6e90\u7801\uff1a<\/p>\n\n\n\n
public Optional<T> filter(Predicate<? super T> predicate) {\n    Objects.requireNonNull(predicate);\n    \/\/\u5982\u679c\u4e3a\u7a7a\u76f4\u63a5\u8fd4\u56dethis\n    if (!isPresent())\n        return this;\n    else\n        \/\/\u5224\u65ad\u8fd4\u56de\u672c\u8eab\u8fd8\u662f\u7a7aOptional\n        return predicate.test(value) ? this : empty();\n}<\/pre>\n\n\n\n
\u7b80\u5355\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nOptional.ofNullable(student).filter(s -> s.getAge()>10);\n<\/pre>\n\n\n\n
Optional.flatMap()\u65b9\u6cd5(Optional\u5bf9\u8c61\u8fdb\u884c\u4e8c\u6b21\u5305\u88c5)<\/strong><\/p>\n\n\n\n
\n\n\n\n
map()\u65b9\u6cd5\u5c06\u5bf9\u5e94Optional< Funcation ><\/code>\u51fd\u6570\u5f0f\u63a5\u53e3\u4e2d\u7684\u5bf9\u8c61\uff0c\u8fdb\u884c\u4e8c\u6b21\u8fd0\u7b97\uff0c\u5c01\u88c5\u6210\u65b0\u7684\u5bf9\u8c61\u7136\u540e\u8fd4\u56de\u5728Optional\u4e2d<\/p>\n\n\n\n
\u6e90\u7801:<\/p>\n\n\n\n
public<U> Optional<U> flatMap(Function<? super T, Optional<U>> mapper) {\n    Objects.requireNonNull(mapper);\n    if (!isPresent())\n        return empty();\n    else {\n        return Objects.requireNonNull(mapper.apply(value));\n    }\n}\n<\/pre>\n\n\n\n
\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nOptional<Object> optName = Optional.ofNullable(student).map(s -> Optional.ofNullable(s.getName()).orElse(\"name\u4e3a\u7a7a\"));<\/pre>\n\n\n\n
Optional.orElse()\u65b9\u6cd5(\u4e3a\u7a7a\u8fd4\u56de\u5bf9\u8c61)<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u5e38\u7528\u65b9\u6cd5\u4e4b\u4e00\uff0c\u8fd9\u4e2a\u65b9\u6cd5\u610f\u601d\u662f\u5982\u679c\u5305\u88c5\u5bf9\u8c61\u4e3a\u7a7a\u7684\u8bdd\uff0c\u5c31\u6267\u884corElse\u65b9\u6cd5\u91cc\u7684value\uff0c\u5982\u679c\u975e\u7a7a\uff0c\u5219\u8fd4\u56de\u5199\u5165\u5bf9\u8c61<\/p>\n\n\n\n
\u6e90\u7801:<\/p>\n\n\n\n
public T orElse(T other) {\n    \/\/\u5982\u679c\u975e\u7a7a\uff0c\u8fd4\u56devalue\uff0c\u5982\u679c\u4e3a\u7a7a\uff0c\u8fd4\u56deother\n    return value != null ? value : other;\n}<\/pre>\n\n\n\n
\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
Student student = new Student();\nstudent.setAge(18);\nOptional.ofNullable(student).orElse(new Student(\"\u5c0f\u660e\", 12));<\/pre>\n\n\n\n
Optional.orElseGet()\u65b9\u6cd5(\u4e3a\u7a7a\u8fd4\u56deSupplier\u5bf9\u8c61)<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u8fd9\u4e2a\u4e0eorElse\u5f88\u76f8\u4f3c\uff0c\u5165\u53c2\u4e0d\u4e00\u6837\uff0c\u5165\u53c2\u4e3aSupplier\u5bf9\u8c61\uff0c\u4e3a\u7a7a\u8fd4\u56de\u4f20\u5165\u5bf9\u8c61\u7684.get()\u65b9\u6cd5\uff0c\u5982\u679c\u975e\u7a7a\u5219\u8fd4\u56de\u5f53\u524d\u5bf9\u8c61\u3002<\/p>\n\n\n\n
\u6e90\u7801:<\/p>\n\n\n\n
public T orElseGet(Supplier<? extends T> other) {\n    return value != null ? value : other.get();\n}<\/pre>\n\n\n\n
\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
Optional<Supplier<Student>> sup=Optional.ofNullable(Student::new);\n\/\/\u8c03\u7528get()\u65b9\u6cd5\uff0c\u6b64\u65f6\u624d\u4f1a\u8c03\u7528\u5bf9\u8c61\u7684\u6784\u9020\u65b9\u6cd5\uff0c\u5373\u83b7\u5f97\u5230\u771f\u6b63\u5bf9\u8c61\nOptional.ofNullable(student).orElseGet(sup.get());\n<\/pre>\n\n\n\n
Suppiler\u662f\u4e00\u4e2a\u63a5\u53e3\uff0c\u662f\u7c7b\u4f3cSpring\u7684\u61d2\u52a0\u8f7d\uff0c\u58f0\u660e\u4e4b\u540e\u5e76\u4e0d\u4f1a\u5360\u7528\u5185\u5b58\uff0c\u53ea\u6709\u6267\u884c\u4e86get()\u65b9\u6cd5\u4e4b\u540e\uff0c\u624d\u4f1a\u8c03\u7528\u6784\u9020\u65b9\u6cd5\u521b\u5efa\u51fa\u5bf9\u8c61 \u521b\u5efa\u5bf9\u8c61\u7684\u8bed\u6cd5\u7684\u8bdd\u5c31\u662fSupplier supStudent= Student::new;<\/code> \u9700\u8981\u4f7f\u7528\u65f6supStudent.get()<\/code>\u5373\u53ef<\/p>\n\n\n\n
Optional.orElseThrow()\u65b9\u6cd5(\u4e3a\u7a7a\u8fd4\u56de\u5f02\u5e38)<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u65b9\u6cd5\u4f5c\u7528\u7684\u8bdd\u5c31\u662f\u5982\u679c\u4e3a\u7a7a\uff0c\u5c31\u629b\u51fa\u4f60\u5b9a\u4e49\u7684\u5f02\u5e38\uff0c\u5982\u679c\u4e0d\u4e3a\u7a7a\u8fd4\u56de\u5f53\u524d\u5bf9\u8c61\uff0c\u5728\u5b9e\u6218\u4e2d\u6240\u6709\u5f02\u5e38\u80af\u5b9a\u662f\u8981\u5904\u7406\u597d\u7684\uff0c\u4e3a\u4e86\u4ee3\u7801\u7684\u53ef\u8bfb\u6027<\/p>\n\n\n\n
\u6e90\u7801\uff1a<\/p>\n\n\n\n
public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X {\n    if (value != null) {\n        return value;\n    } else {\n        throw exceptionSupplier.get();\n    }\n}<\/pre>\n\n\n\n
\u5b9e\u4f8b\uff1a<\/p>\n\n\n\n
\/\/\u7b80\u5355\u7684\u4e00\u4e2a\u67e5\u8be2\nMember member = memberService.selectByPhone(request.getPhone());\nOptional.ofNullable(member).orElseThrow(() -> new ServiceException(\"\u6ca1\u6709\u67e5\u8be2\u7684\u76f8\u5173\u6570\u636e\"));<\/pre>\n\n\n\n
\u76f8\u4f3c\u65b9\u6cd5\u8fdb\u884c\u5bf9\u6bd4\u5206\u6790<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u53ef\u80fd\u770b\u5230\u8fd9\uff0c\u6ca1\u7528\u7528\u8fc7\u7684\u8bdd\u4f1a\u89c9\u5f97orElse()<\/code>\u548corElseGet()<\/code>\u8fd8\u6709orElseThrow()<\/code>\u5f88\u76f8\u4f3c\uff0cmap()\u548cflatMap()\u597d\u76f8\u4f3c,\u4e0d\u7528\u7740\u6025\uff0c\u90fd\u662f\u4ece\u8fd9\u4e00\u6b65\u8fc7\u6765\u7684\uff0c\u6211\u518d\u7ed9\u5927\u5bb6\u603b\u7ed3\u4e00\u4e0b\u4e0d\u540c\u65b9\u6cd5\u7684\u5f02\u540c\u70b9 orElse()<\/code>\u548corElseGet()<\/code>\u548corElseThrow()<\/code>\u7684\u5f02\u540c\u70b9<\/p>\n\n\n\n
\u65b9\u6cd5\u6548\u679c\u7c7b\u4f3c\uff0c\u5982\u679c\u5bf9\u8c61\u4e0d\u4e3a\u7a7a\uff0c\u5219\u8fd4\u56de\u5bf9\u8c61\uff0c\u5982\u679c\u4e3a\u7a7a\uff0c\u5219\u8fd4\u56de\u65b9\u6cd5\u4f53\u4e2d\u7684\u5bf9\u5e94\u53c2\u6570\uff0c\u6240\u4ee5\u53ef\u4ee5\u770b\u51fa\u8fd9\u4e09\u4e2a\u65b9\u6cd5\u4f53\u4e2d\u53c2\u6570\u662f\u4e0d\u4e00\u6837\u7684 orElse\uff08T \u5bf9\u8c61\uff09 orElseGet\uff08Supplier < T ><\/code>\u5bf9\u8c61\uff09 orElseThrow\uff08\u5f02\u5e38\uff09<\/p>\n\n\n\n
map()\u548corElseGet\u7684\u5f02\u540c\u70b9<\/strong><\/p>\n\n\n\n
\u65b9\u6cd5\u6548\u679c\u7c7b\u4f3c\uff0c\u5bf9\u65b9\u6cd5\u53c2\u6570\u8fdb\u884c\u4e8c\u6b21\u5305\u88c5\uff0c\u5e76\u8fd4\u56de,\u5165\u53c2\u4e0d\u540c map\uff08function\u51fd\u6570\uff09 flatmap\uff08Optional< function ><\/code>\u51fd\u6570\uff09<\/p>\n\n\n\n
\u5177\u4f53\u8981\u600e\u4e48\u7528\uff0c\u8981\u6839\u636e\u4e1a\u52a1\u573a\u666f\u4ee5\u53ca\u4ee3\u7801\u89c4\u8303\u6765\u5b9a\u4e49\uff0c\u4e0b\u9762\u53ef\u4ee5\u7b80\u5355\u770b\u4e00\u4e0b\u6211\u5728\u5b9e\u6218\u4e2d\u600e\u7528\u4f7f\u7528\u795e\u5947\u7684Optional\u3002<\/p>\n\n\n\n
\u5b9e\u6218\u573a\u666f<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u573a\u666f1\uff1a\u5728service\u5c42\u4e2d \u67e5\u8be2\u4e00\u4e2a\u5bf9\u8c61\uff0c\u8fd4\u56de\u4e4b\u540e\u5224\u65ad\u662f\u5426\u4e3a\u7a7a\u5e76\u505a\u5904\u7406<\/p>\n\n\n\n
\/\/\u67e5\u8be2\u4e00\u4e2a\u5bf9\u8c61\nMember member = memberService.selectByIdNo(request.getCertificateNo());\n\/\/\u4f7f\u7528ofNullable\u52a0orElseThrow\u505a\u5224\u65ad\u548c\u64cd\u4f5c\nOptional.ofNullable(member).orElseThrow(() -> new ServiceException(\"\u6ca1\u6709\u67e5\u8be2\u7684\u76f8\u5173\u6570\u636e\"));<\/pre>\n\n\n\n
\u573a\u666f2\uff1a\u6211\u4eec\u53ef\u4ee5\u5728dao\u63a5\u53e3\u5c42\u4e2d\u5b9a\u4e49\u8fd4\u56de\u503c\u65f6\u5c31\u52a0\u4e0aOptional<\/p>\n\n\n\n
public interface LocationRepository extends JpaRepository<Location, String> {\nOptional<Location> findLocationById(String id);\n}<\/pre>\n\n\n\n
\u7136\u5728\u662fService\u4e2d<\/p>\n\n\n\n
public TerminalVO findById(String id) {\n    \/\/\u8fd9\u4e2a\u65b9\u6cd5\u5728dao\u5c42\u4e5f\u662f\u7528\u4e86Optional\u5305\u88c5\u4e86\n    Optional<Terminal> terminalOptional = terminalRepository.findById(id);\n    \/\/\u76f4\u63a5\u4f7f\u7528isPresent()\u5224\u65ad\u662f\u5426\u4e3a\u7a7a\n    if (terminalOptional.isPresent()) {\n    \/\/\u4f7f\u7528get()\u65b9\u6cd5\u83b7\u53d6\u5bf9\u8c61\u503c\n        Terminal terminal = terminalOptional.get();\n        \/\/\u5728\u5b9e\u6218\u4e2d\uff0c\u6211\u4eec\u5df2\u7ecf\u514d\u53bb\u4e86\u7528set\u53bb\u8d4b\u503c\u7684\u7e41\u7410\uff0c\u76f4\u63a5\u7528BeanCopy\u53bb\u8d4b\u503c\n        TerminalVO terminalVO = BeanCopyUtils.copyBean(terminal, TerminalVO.class);\n        \/\/\u8c03\u7528dao\u5c42\u65b9\u6cd5\u8fd4\u56de\u5305\u88c5\u540e\u7684\u5bf9\u8c61\n        Optional<Location> location = locationRepository.findLocationById(terminal.getLocationId());\n        if (location.isPresent()) {\n            terminalVO.setFullName(location.get().getFullName());\n        }\n        return terminalVO;\n    }\n    \/\/\u4e0d\u8981\u5fd8\u8bb0\u629b\u51fa\u5f02\u5e38\n    throw new ServiceException(\"\u8be5\u7ec8\u7aef\u4e0d\u5b58\u5728\");\n}\n<\/pre>\n\n\n\n
\u5b9e\u6218\u573a\u666f\u8fd8\u6709\u5f88\u591a\uff0c\u5305\u62ecreturn\u65f6\u53ef\u4ee5\u5224\u65ad\u662f\u5426\u8fd4\u56de\u5f53\u524d\u503c\u8fd8\u662f\u8df3\u8f6c\u5230\u53e6\u4e00\u4e2a\u65b9\u6cd5\u4f53\u4e2d\uff0c\u5176\u5b83\u7684\u8fd8\u6709\u5f88\u591a\u3002<\/p>\n\n\n\n
Optional\u4f7f\u7528\u6ce8\u610f\u4e8b\u9879<\/strong><\/p>\n\n\n\n
\n\n\n\n
Optional\u771f\u4e48\u597d\u7528\uff0c\u771f\u7684\u53ef\u4ee5\u5b8c\u5168\u66ff\u4ee3if\u5224\u65ad\u5417\uff1f\u6211\u60f3\u8fd9\u80af\u5b9a\u662f\u5927\u5bb6\u4f7f\u7528\u5b8c\u4e4b\u540eOptional\u4e4b\u540e\u53ef\u80fd\u4f1a\u4ea7\u751f\u7684\u60f3\u6cd5\uff0c\u7b54\u6848\u662f\u5426\u5b9a\u7684 \u4e3e\u4e00\u4e2a\u6700\u7b80\u5355\u7684\u6817\u5b50\uff1a<\/p>\n\n\n\n
\u4f8b\u5b50\uff1a\u5982\u679c\u6211\u53ea\u60f3\u5224\u65ad\u5bf9\u8c61\u7684\u67d0\u4e00\u4e2a\u53d8\u91cf\u662f\u5426\u4e3a\u7a7a\u5e76\u4e14\u505a\u51fa\u5224\u65ad\u5462\uff1f<\/p>\n\n\n\n
Person person=new Person();\nperson.setName(\"\");\npersion.setAge(2);\n\/\/\u666e\u901a\u5224\u65ad\nif(StringUtils.isNotBlank(person.getName())){\n   \/\/\u540d\u79f0\u4e0d\u4e3a\u7a7a\u6267\u884c\u4ee3\u7801\u5757\n}\n\/\/\u4f7f\u7528Optional\u505a\u5224\u65ad\nOptional.ofNullable(person).map(p -> p.getName()).orElse(\"name\u4e3a\u7a7a\");<\/pre>\n\n\n\n
\u6211\u89c9\u5f97\u8fd9\u4e2a\u4f8b\u5b50\u5c31\u80fd\u5f88\u597d\u7684\u8bf4\u660e\u8fd9\u4e2a\u95ee\u9898\uff0c\u53ea\u662f\u4e00\u4e2a\u5f88\u7b80\u5355\u5224\u65ad\uff0c\u5982\u679c\u7528\u4e86Optional\u6211\u4eec\u8fd8\u9700\u8981\u8003\u8651\u5305\u88c5\u503c\uff0c\u8003\u8651\u4ee3\u7801\u4e66\u5199\uff0c\u8003\u8651\u65b9\u6cd5\u8c03\u7528\uff0c\u867d\u7136\u53ea\u6709\u4e00\u884c\uff0c\u4f46\u662f\u53ef\u8bfb\u6027\u5e76\u4e0d\u597d\uff0c\u5982\u679c\u522b\u7684\u7a0b\u5e8f\u5458\u53bb\u8bfb\uff0c\u6211\u89c9\u5f97\u80af\u5b9a\u6ca1\u6709if\u770b\u7684\u660e\u663e\u3002<\/p>\n\n\n\n
Jdk 9\u5bf9Optional\u4f18\u5316<\/strong><\/p>\n\n\n\n
\n\n\n\n
\u9996\u5148\u589e\u52a0\u4e86\u4e09\u4e2a\u65b9\u6cd5: or()<\/code>\u3001ifPresentOrElse()<\/code> \u548c stream()<\/code>\u3002or() \u4e0eorElse\u7b49\u65b9\u6cd5\u76f8\u4f3c\uff0c\u5982\u679c\u5bf9\u8c61\u4e0d\u4e3a\u7a7a\u8fd4\u56de\u5bf9\u8c61\uff0c\u5982\u679c\u4e3a\u7a7a\u5219\u8fd4\u56deor()\u65b9\u6cd5\u4e2d\u9884\u8bbe\u7684\u503c\u3002<\/p>\n\n\n\n
ifPresentOrElse()<\/code> \u65b9\u6cd5\u6709\u4e24\u4e2a\u53c2\u6570\uff1a\u4e00\u4e2a Consumer \u548c\u4e00\u4e2a Runnable\u3002\u5982\u679c\u5bf9\u8c61\u4e0d\u4e3a\u7a7a\uff0c\u4f1a\u6267\u884c Consumer \u7684\u52a8\u4f5c\uff0c\u5426\u5219\u8fd0\u884c Runnable\u3002\u76f8\u6bd4ifPresent()<\/code>\u591a\u4e86OrElse\u5224\u65ad\u3002stream()<\/code>\u5c06Optional\u8f6c\u6362\u6210stream\uff0c\u5982\u679c\u6709\u503c\u5c31\u8fd4\u56de\u5305\u542b\u503c\u7684stream\uff0c\u5982\u679c\u6ca1\u503c\uff0c\u5c31\u8fd4\u56de\u7a7a\u7684stream\u3002<\/p>\n\n\n\n
\u4ee5\u4e0a\u5c31\u662fJava8\u4e2d\u65b0\u5224\u7a7a\u65b9\u6cd5\u4e4bOptional\u7c7b\u7684\u4f7f\u7528\u8be6\u89e3\u7684\u8be6\u7ec6\u5185\u5bb9\uff0c\u66f4\u591a\u5173\u4e8eJava8 Optional\u7c7b\u7684\u8d44\u6599\u8bf7\u5173\u6ce8\u5176\u5b83\u76f8\u5173\u6587\u7ae0\uff01<\/p>\n\n\n\n
\u539f\u6587\u5730\u5740\uff1ahttps:\/\/blog.csdn.net\/weixin_45581915\/article\/details\/124493863<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
\u8ba4\u8bc6Optional Opitonal\u7c7b\u5c31\u662fJava\u63d0\u4f9b\u7684\u4e3a\u4e86\u89e3\u51b3\u5927\u5bb6\u5e73\u65f6\u5224\u65ad\u5bf9\u8c61\u662f\u5426\u4e3a\u7a7a\u7528\uff0c\u901a\u5e38\u4f1a\u7528 nul […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"_links":{"self":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/12559"}],"collection":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=12559"}],"version-history":[{"count":2,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/12559\/revisions"}],"predecessor-version":[{"id":12563,"href":"https:\/\/92it.top\/index.php?rest_route=\/wp\/v2\/posts\/12559\/revisions\/12563"}],"wp:attachment":[{"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12559"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12559"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/92it.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}