一步一步

public class ParallelStreams {
    public static long sequentialSum(long n) {
        return Stream.iterate(1L, i->i+1)
                .limit(n)
                .reduce(0L, Long::sum);
    }

    public static long iterativeSum(long n) {
        long result = 0;
        for (long i = 1L; i <= n; i++) {
            result += i;
        }
        return result;
    }

    public static long parallelSum(long n) {
        return Stream.iterate(1L, i->i+1)
                .limit(n)
                .parallel()
                .reduce(0L, Long::sum);
    }
}

public static long measureSumPerf(Function<Long, Long> adder, long n) {
    long fastest = Long.MAX_VALUE;
    for (int i = 0; i < 10; i++) {
        long start = System.nanoTime();
        long sum = adder.apply(n);
        long duration = (System.nanoTime() - start) / 1_000_000; //毫秒
        System.out.println("Result: "+sum);
        if(duration < fastest) fastest = duration;
    }
    return fastest;
}

public static void main(String[] args) {
    System.out.println("顺序流:" + measureSumPerf(ParallelStreams::sequentialSum, 10_000_000)+" 毫秒");
    System.out.println("循环:" + measureSumPerf(ParallelStreams::iterativeSum, 10_000_000)+" 毫秒");
    System.out.println("并行流:" + measureSumPerf(ParallelStreams::parallelSum, 10_000_000)+" 毫秒");
}

import static spark.Spark.get;
public class Main {
    public static void main(String[] args) {
        get("/hello", (req, res) -> "Hello World");
        get("/", (req, res) -> "欢迎");
    }
}

//Book.java
public class Book {
    private String mTitle;
    private String mAuthor;
    private int mPublicationDate;

    public Book(String title, String author, int publicationDate) {
        mTitle = title;
        mAuthor = author;
        mPublicationDate = publicationDate;
    }

    public String getTitle() {
        return mTitle;
    }

    public String getAuthor() {
        return mAuthor;
    }

    public int getPublicationDate() {
        return mPublicationDate;
    }

    @Override
    public String toString() {
        return "Book{" +
                "mTitle='" + mTitle + '\'' +
                ", mAuthor='" + mAuthor + '\'' +
                ", mPublicationDate=" + mPublicationDate +
                '}';
    }
}

//Books.java
import java.util.ArrayList;
import java.util.List;

public class Books {
    public static List<Book> all() {
        List<Book> books = new ArrayList<Book>();
        books.add(new Book("Functional Programming in Java", "Venkat Subramaniam", 2014));
        books.add(new Book("Clean Code", "Robert C. Martin", 2008));
        books.add(new Book("Java Generics and Collections", "Maurice Naftalin and Philip Wadler", 2008));
        books.add(new Book("Effective Java", "Joshua Bloch", 2008));
        books.add(new Book("Pragmatic Unit Testing in Java 8 with JUnit", "Jeff Langr", 2015));
        books.add(new Book("JavaFX Essentials", "Mohamed Taman", 2015));
        return books;
    }
}

public class Main {

    public static void usingAnonymousInlineClass(){
        List<Book> books = Books.all();
        Collections.sort(books, new Comparator<Book>() {
            @Override
            public int compare(Book b1, Book b2) {
                return b1.getTitle().compareTo(b2.getTitle());
            }
        });
        for(Book book : books) {
            System.out.println(book);
        }
    }

    public static void main(String[] args) {
        // write your code here
        usingAnonymousInlineClass();
    }
}

//Lambda长形式
public static void usingLambdaInLongForm(){
    List<Book> books = Books.all();
    Collections.sort(books, (Book b1, Book b2) -> {
        return b1.getTitle().compareTo(b2.getTitle());
    });
    for(Book book : books) {
        System.out.println(book);
    }
}

//Lambda短形式
public static void usingLambdaInShortForm(){
    List<Book> books = Books.all();
    Collections.sort(books, (b1, b2) -> b1.getTitle().compareTo(b2.getTitle()));
    //forEach调用
    books.forEach((book)->System.out.println(book));
}

public static void usingMethodReference(){
    List<Book> books = Books.all();
    Collections.sort(books, Comparator.comparing(Book::getTitle));
    books.forEach(System.out::println);
}

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import java.util.List;
import java.util.ArrayList;

public class JdbcMain {
  public static void main(String[] args) throws ClassNotFoundException {
    // TODO: Load the SQLite JDBC driver (JDBC class implements java.sql.Driver)
    Class.forName("org.sqlite.JDBC");
    // TODO: Create a DB connection
    try(Connection connection = DriverManager.getConnection("jdbc:sqlite:contactmgr.db")) {
      
      // TODO: Create a SQL statement
      Statement statement = connection.createStatement();
      
      // TODO: Create a DB table
      statement.executeUpdate("DROP TABLE IF EXISTS contacts");
      statement.executeUpdate("CREATE TABLE contacts (id INTEGER PRIMARY KEY, firstname STRING, lastname STRING, email STRING, phone INT(10))");
      
      // TODO: Insert a couple contacts
      statement.executeUpdate("INSERT INTO contacts (firstname, lastname, email, phone) VALUES('Liu', 'Lixiang', 'liulixiang1988@gmail.com', 1234567890)");
      statement.executeUpdate("INSERT INTO contacts (firstname, lastname, email, phone) VALUES('Long', 'Long', 'abc@gmail.com', 0987654321)");
      
      // TODO: Fetch all the records from the contacts table
      ResultSet rs = statement.executeQuery("SELECT * FROM contacts");
      
      // TODO: Iterate over the ResultSet & display contact info
      while(rs.next()){
        int id = rs.getInt("id");
        String firstName = rs.getString("firstname");
        String lastName = rs.getString("lastname");
        
        System.out.printf("%s %s (%d)", firstName, lastName, id);
      }
      
    } catch (SQLException ex) {
      // Display connection or query errors
      System.err.printf("There was a database error: %s%n",ex.getMessage());
    }
  }
}