java

whatsmars-common/src/test/java/org/hongxi/java/util/Java8Test.java

+package org.hongxi.java.util;
+
+import org.junit.Test;
+
+import javax.script.ScriptEngine;
+import javax.script.ScriptEngineManager;
+import javax.script.ScriptException;
+import java.nio.charset.StandardCharsets;
+import java.time.*;
+import java.util.Base64;
+
+public class Java8Test {
+
+    @Test
+    public void join() {
+        String[] countries = {"China", "America", "Japan"};
+        System.out.println(String.join(",", countries));
+    }
+
+    @Test
+    public void base64() {
+        String text = "Base64 finally in Java 8!";
+        String encoded = Base64
+                .getEncoder()
+                .encodeToString(text.getBytes(StandardCharsets.UTF_8));
+        System.out.println(encoded);
+
+        String decoded = new String(Base64.getDecoder().decode(encoded), StandardCharsets.UTF_8);
+        System.out.println(decoded);
+    }
+
+    @Test
+    public void script() throws ScriptException {
+        ScriptEngineManager manager = new ScriptEngineManager();
+        ScriptEngine engine = manager.getEngineByName("JavaScript");
+        System.out.println(engine.getClass().getName());
+        System.out.println("Result:" + engine.eval("function f() { return 1; }; f() + 1;"));
+    }
+
+    @Test
+    public void clock() {
+        Clock clock = Clock.systemUTC();
+        System.out.println(clock.instant());
+        System.out.println(clock.millis());
+        LocalDate localDate = LocalDate.now(); // LocalDate.now(clock)
+        System.out.println(localDate);
+        LocalTime localTime = LocalTime.now(); // LocalTime.now(clock)
+        System.out.println(localTime);
+        LocalDateTime localDateTime = LocalDateTime.now(); // LocalDateTime.now(clock)
+        System.out.println(localDateTime);
+
+        LocalDateTime from = LocalDateTime.of( 2014, Month.APRIL, 16, 0, 0, 0 );
+        LocalDateTime to = LocalDateTime.of( 2015, Month.APRIL, 16, 23, 59, 59 );
+        Duration duration = Duration.between(from, to);
+        System.out.println("Duration in days: " + duration.toDays());
+        System.out.println("Duration in hours: " + duration.toHours());
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/LambdaTests.java

+package org.hongxi.java.util;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.ThreadLocalRandom;
+
+/**
+ * Created by javahongxi on 2018/1/2.
+ */
+public class LambdaTests {
+
+    @Test
+    public void t() {
+        new Thread(() -> System.out.println("Hi, I am lambda!")).start();
+        System.out.println("main thread ...");
+    }
+
+    @Test
+    public void t2() {
+        Arrays.asList("a", "b", "c").forEach(e -> System.out.println(e));
+    }
+
+    @Test
+    public void t3() {
+        Arrays.asList("a", "b", "c").forEach(e -> {
+            System.out.println(System.currentTimeMillis());
+            System.out.println(e);
+        });
+    }
+
+    @Test
+    public void t4() {
+        List<String> names = new ArrayList<>();
+        names.add("d");
+        names.add("a");
+        names.add("ax");
+        names.add("bbb");
+        names.sort(String::compareTo);
+        System.out.println(names);
+    }
+
+    @Test
+    public void t5() {
+        Optional<String> fullName = Optional.ofNullable(null);
+        System.out.println("Full Name is set? " + fullName.isPresent());
+        System.out.println("Full Name: " + fullName.orElseGet(() -> "[none]"));
+        System.out.println(fullName.map(s -> "Hey " + s + "!").orElse("Hey Stranger!"));
+    }
+
+    @Test
+    public void t6() {
+        long[] arr = new long [20000];
+
+        Arrays.parallelSetAll(arr,
+                index -> ThreadLocalRandom.current().nextInt(1000000));
+        Arrays.stream(arr).limit(10).forEach(
+                i -> System.out.print(i + " "));
+        System.out.println();
+
+        Arrays.parallelSort(arr);
+        Arrays.stream(arr).limit(10).forEach(
+                i -> System.out.print(i + " "));
+        System.out.println();
+    }
+
+}

whatsmars-common/src/test/java/org/hongxi/java/util/function/CollectionFactory.java

+package org.hongxi.java.util.function;
+
+import java.util.function.Supplier;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public interface CollectionFactory {
+
+    static MyCollection create(Supplier<MyCollection> supplier) {
+        return supplier.get();
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/function/MyCollection.java

+package org.hongxi.java.util.function;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public interface MyCollection {
+
+    int size();
+
+    default String notRequired() {
+        return "Default implementation";
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/function/MyList.java

+package org.hongxi.java.util.function;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public class MyList implements MyCollection {
+    @Override
+    public int size() {
+        return 0;
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/function/NewList.java

+package org.hongxi.java.util.function;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public class NewList implements MyCollection {
+    @Override
+    public int size() {
+        return 0;
+    }
+
+    @Override
+    public String notRequired() {
+        return "Overridden implementation";
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/function/Test.java

+package org.hongxi.java.util.function;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public class Test {
+    public static void main(String[] args) {
+        MyCollection collection = CollectionFactory.create(MyList::new);
+        System.out.println(collection.notRequired());
+
+        collection = CollectionFactory.create(NewList::new);
+        System.out.println(collection.notRequired());
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/stream/Status.java

+package org.hongxi.java.util.stream;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public enum Status {
+    OPEN, CLOSED
+}

whatsmars-common/src/test/java/org/hongxi/java/util/stream/StreamTest.java

+package org.hongxi.java.util.stream;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.stream.IntStream;
+
+/**
+ * Created by shenhongxi on 2019/4/10.
+ */
+public class StreamTest {
+
+    public static void main(String[] args) {
+        System.setProperty("java.util.concurrent.ForkJoinPool.common.parallelism", "10");
+        CopyOnWriteArrayList<Integer> numbers = new CopyOnWriteArrayList<>();
+        IntStream.range(0, 10000).parallel().forEach(numbers::add);
+        System.out.println(numbers.size() == 10000);
+
+        // 下面的操作会报错 ArrayIndexOutOfBoundsException
+        List<Integer> list2 = new ArrayList<>();
+        numbers.parallelStream().forEach(list2::add);
+        System.out.println(list2.size() == numbers.size());
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/stream/StreamTests.java

+package org.hongxi.java.util.stream;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.stream.Collectors;
+
+/**
+ * Created by shenhongxi on 2019/4/14.
+ */
+public class StreamTests {
+
+    @Test
+    public void t() {
+        List<String> words = new ArrayList<>();
+        words.add("a");
+        words.add("b");
+        words.add("c");
+        words = words.stream().filter(e -> e.equals("d")).collect(Collectors.toList());
+        assert words.isEmpty();
+    }
+
+    @Test
+    public void t2() {
+        List<String> words = new ArrayList<>();
+        words.add("a");
+        words.add("b");
+        words.add("c");
+        CopyOnWriteArrayList<String> result = new CopyOnWriteArrayList<>();
+        words.parallelStream().forEach(e -> result.add(e.toUpperCase()));
+        assert result.size() == words.size();
+    }
+
+    @Test
+    public void t3() {
+        List<String> words = new ArrayList<>();
+        words.add("a");words.add("b");words.add("c");words.add("d");words.add("e");words.add("f");
+        words.add("g");words.add("h");words.add("i");words.add("j");words.add("k");words.add("l");
+        words.add("m");words.add("n");words.add("o");words.add("p");words.add("q");words.add("r");
+        words.add("s");words.add("t");words.add("u");words.add("v");words.add("w");words.add("x");
+        words.add("y");words.add("z");
+        Map<String, String> result = words.parallelStream()
+                .collect(HashMap::new, (m, word) -> m.put(word, word.toUpperCase()), HashMap::putAll);
+        System.out.println(result);
+        assert result.size() == words.size();
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/stream/Task.java

+package org.hongxi.java.util.stream;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public class Task {
+    private Status status;
+    private int point;
+
+    public Task() {
+    }
+
+    public Task(Status status, int point) {
+        this.status = status;
+        this.point = point;
+    }
+
+    public Status getStatus() {
+        return status;
+    }
+
+    public void setStatus(Status status) {
+        this.status = status;
+    }
+
+    public int getPoint() {
+        return point;
+    }
+
+    public void setPoint(int point) {
+        this.point = point;
+    }
+
+    @Override
+    public String toString() {
+        return String.format("(%s, %d)", status, point);
+    }
+}

whatsmars-common/src/test/java/org/hongxi/java/util/stream/Test.java

+package org.hongxi.java.util.stream;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+import static java.util.stream.Collectors.*;
+
+/**
+ * Created by shenhongxi on 2018/1/11.
+ */
+public class Test {
+    public static void main(String[] args) {
+        Collection<Task> tasks = Arrays.asList(
+                new Task(Status.OPEN, 5),
+                new Task(Status.OPEN, 13),
+                new Task(Status.CLOSED, 8)
+        );
+        int openTaskPoints = tasks
+                .stream()
+                .filter(task -> task.getStatus() == Status.OPEN)
+                .mapToInt(Task::getPoint)
+                .sum();
+        System.out.println(openTaskPoints);
+
+        final int totalPoints = tasks
+                .stream()
+                .parallel()
+                .map(Task::getPoint)
+                .reduce(0, Integer::sum);
+        System.out.println(totalPoints);
+
+        Map<Status, List<Task>> map = tasks.stream().collect(groupingBy(Task::getStatus));
+        System.out.println(map);
+        Map<Status, Long> map2 = tasks.stream().collect(groupingBy(Task::getStatus, counting()));
+        System.out.println(map2);
+        Map<Boolean, List<Task>> map3 = tasks.stream().collect(partitioningBy(e -> e.getPoint() > 7));
+        System.out.println(map3);
+//        Map<String, Product> productMap = products.stream().collect(toMap(Product::getSku, identity(), (key1, key2) -> key2));
+
+        Collection<String> result = tasks
+                .stream()
+                .mapToInt(Task::getPoint)
+                .mapToDouble(point -> point * 100 / totalPoints)
+                .mapToObj(percentage -> (int) percentage + "%")
+                .collect(toList());
+        System.out.println(result);
+    }
+}