64 lines
1.8 KiB
Java
64 lines
1.8 KiB
Java
// streams/Optionals.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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import java.util.*;
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import java.util.stream.*;
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import java.util.function.*;
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public class Optionals {
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static void basics(Optional<String> optString) {
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if(optString.isPresent())
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System.out.println(optString.get());
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else
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System.out.println("Nothing inside!");
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}
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static void if_present(Optional<String> optString) {
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optString.ifPresent(System.out::println);
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}
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static void or_else(Optional<String> optString) {
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System.out.println(optString.orElse("Nada"));
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}
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static void or_else_get(Optional<String> optString) {
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System.out.println(
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optString.orElseGet(() -> "Generated"));
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}
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static void or_else_throw(Optional<String> optString) {
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try {
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System.out.println(optString.orElseThrow(
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() -> new Exception("Supplied")));
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} catch(Exception e) {
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System.out.println("Caught " + e);
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}
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}
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static void
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test(String testName, Consumer<Optional<String>> cos) {
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System.out.println(" === " + testName + " === ");
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cos.accept(Stream.of("Epithets").findFirst());
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cos.accept(Stream.<String>empty().findFirst());
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}
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public static void main(String[] args) {
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test("basics", Optionals::basics);
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test("ifPresent", Optionals::if_present);
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test("orElse", Optionals::or_else);
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test("orElseGet", Optionals::or_else_get);
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test("orElseThrow", Optionals::or_else_throw);
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}
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}
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/* Output:
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=== basics ===
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Epithets
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Nothing inside!
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=== ifPresent ===
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Epithets
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=== orElse ===
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Epithets
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Nada
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=== orElseGet ===
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Epithets
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Generated
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=== orElseThrow ===
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Epithets
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Caught java.lang.Exception: Supplied
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*/
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