public class BaseTest {
/* 转载：https://blog.csdn.net/u013291394/article/details/52662761
git: https://github.com/shekhargulati/java8-the-missing-tutorial/tree/master/code
*/
public static void main(String[] args) {
BaseTest tt = new BaseTest();
// tt.titleSummary(DataUtils.getTasks());
tt.taskTest1();
}
public void taskTest1() {
List<Task> tasks = DataUtils.getTasks();
Map<TaskType, List<Task>> allTasksByType = new HashMap<>();
for (Task task : tasks) {
List<Task> existingTasksByType = allTasksByType.get(task.getType());
if (existingTasksByType == null) {
List<Task> tasksByType = new ArrayList<>();
tasksByType.add(task);
allTasksByType.put(task.getType(), tasksByType);
} else {
existingTasksByType.add(task);
}
}
for (Map.Entry<TaskType, List<Task>> entry : allTasksByType.entrySet()) {
System.out.println(String.format("%s =>> %s", entry.getKey(), entry.getValue()));
}
//生成统计信息
IntSummaryStatistics summaryStatistics = tasks.stream().map(Task::getTitle).collect(summarizingInt(String::length));
System.out.println(summaryStatistics.getAverage()); //32.4
System.out.println(summaryStatistics.getCount()); //5
System.out.println(summaryStatistics.getMax()); //44
System.out.println(summaryStatistics.getMin()); //24
System.out.println(summaryStatistics.getSum()); //162
}
//找到拥有最长标题的任务
public Task taskWithLongestTitle(List<Task> tasks) {
//// Optional<Task> collect = tasks.stream().collect(Collectors.maxBy(Comparator.comparingInt(t -> t.getTitle().length())) );
// Optional<Task> collect = tasks.stream().collect(maxBy(Comparator.comparingInt(t -> t.getTitle().length())));
//// Optional<Task> collect = tasks.stream().collect(maxBy((t1, t2) -> t1.getTitle().length() - t2.getTitle().length()));
// Task task = collect.get();
// return task;
Task collect = tasks.stream().collect(collectingAndThen(maxBy((t1, t2) -> t1.getTitle().length() - t2.getTitle().length()), Optional::get));
System.out.println(collect.getTitle());
return collect;
}
//分割
private static Map<Boolean, List<Task>> partitionOldAndFutureTasks(List<Task> tasks) {
return tasks.stream().collect(partitioningBy(task -> task.getDueOn().isAfter(LocalDate.now())));
}
//统计标签的总数
public int totalTagCount(List<Task> tasks) {
Integer collect = tasks.stream().collect(summingInt(task -> task.getTags().size()));
System.out.println("BaseTest.totalTagCount: "+collect);
return collect;
}
//分类收集器
//例子1：根据类型对任务分类
private static Map<TaskType, List<Task>> groupTasksByType(List<Task> tasks) {
return tasks.stream().collect(groupingBy(Task::getType));
}
//例子2：根据标签分类
private static Map<String, List<Task>> groupingByTag(List<Task> tasks) {
return tasks.stream().
flatMap(task -> task.getTags().stream().map(tag -> new TaskTag(tag, task))).
collect(groupingBy(TaskTag::getTag, mapping(TaskTag::getTask,toList())));
}
//例子3：根据标签和数量对任务分类
private static Map<String, Long> tagsAndCount(List<Task> tasks) {
return tasks.stream().
flatMap(task -> task.getTags().stream().map(tag -> new TaskTag(tag, task))).
collect(groupingBy(TaskTag::getTag, counting()));
}
//例子4：根据任务类型和创建日期分类
private static Map<TaskType, Map<LocalDate, List<Task>>> groupTasksByTypeAndCreationDate(List<Task> tasks) {
return tasks.stream().collect(groupingBy(Task::getType, groupingBy(Task::getCreatedOn)));
}
//简单-生成任务标题的概述
public String titleSummary(List<Task> tasks) {
return tasks.stream().map(Task::getTitle).collect(joining(";"));
}
//实体：
public static enum TaskType {
READING, CODING, BLOGGING
}
//bean
public static class Task {
private LocalDate dueOn;
private final String id;
private final String title;
private final String description;
private final TaskType type;
private LocalDate createdOn;
private Set<String> tags = new HashSet<>();
public Task(final String id, final String title, final TaskType type) {
this.id = id;
this.title = title;
this.description = title;
this.type = type;
this.createdOn = LocalDate.now();
}
public Task(final String title, final TaskType type) {
this(title, title, type, LocalDate.now());
}
public Task(final String title, final TaskType type, final LocalDate createdOn) {
this(title, title, type, createdOn);
}
public Task(final String title, final String description, final TaskType type, final LocalDate createdOn) {
this.id = UUID.randomUUID().toString();
this.title = title;
this.description = description;
this.type = type;
this.createdOn = createdOn;
}
public LocalDate getDueOn() {
return dueOn;
}
public void setDueOn(LocalDate dueOn) {
this.dueOn = dueOn;
}
public String getId() {
return id;
}
public String getTitle() {
return title;
}
public String getDescription() {
return description;
}
public TaskType getType() {
return type;
}
public LocalDate getCreatedOn() {
return createdOn;
}
public Task addTag(String tag) {
this.tags.add(tag);
return this;
}
public Set<String> getTags() {
return Collections.unmodifiableSet(tags);
}
@Override
public String toString() {
return "Task{" +
"title='" + title + '\'' +
", type=" + type +
'}';
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Task task = (Task) o;
return Objects.equals(title, task.title) &&
Objects.equals(type, task.type);
}
@Override
public int hashCode() {
return Objects.hash(title, type);
}
}
private static class TaskTag {
final String tag;
final Task task;
public TaskTag(String tag, Task task) {
this.tag = tag;
this.task = task;
}
public String getTag() {
return tag;
}
public Task getTask() {
return task;
}
}
public static class DataUtils {
public static Stream<String> lines() {
return filePathToStream("src/main/resources/book.txt");
}
public static Stream<String> negativeWords() {
return filePathToStream("src/main/resources/negative-words.txt");
}
public static Stream<String> filePathToStream(String path) {
try {
return Files.lines(Paths.get("training", path));
} catch (IOException e) {
throw new RuntimeException(e);
}
}
public static IntStream range(int start, int end) {
return IntStream.rangeClosed(start, end);
}
public static List<Task> getTasks() {
Task task1 = new Task("Read Java 8 in action", TaskType.READING, LocalDate.of(2015, Month.SEPTEMBER, 20)).addTag("java").addTag("java8").addTag("books");
Task task2 = new Task("Write factorial program in Haskell", TaskType.CODING, LocalDate.of(2015, Month.SEPTEMBER, 20)).addTag("program").addTag("haskell").addTag("functional");
Task task3 = new Task("Read Effective Java", TaskType.READING, LocalDate.of(2015, Month.SEPTEMBER, 21)).addTag("java").addTag("books");
Task task4 = new Task("Write a blog on Stream API", TaskType.BLOGGING, LocalDate.of(2015, Month.SEPTEMBER, 21)).addTag("writing").addTag("stream").addTag("java8");
Task task5 = new Task("Write prime number program in Scala", TaskType.CODING, LocalDate.of(2015, Month.SEPTEMBER, 22)).addTag("scala").addTag("functional").addTag("program");
return Stream.of(task1, task2, task3, task4, task5).collect(toList());
}
}
}
浙公网安备 33010602011771号