public class Trader{

private String name;
private String city;

public Trader(String n, String c){
this.name = n;
this.city = c;
}

public String getName(){
return this.name;
}

public String getCity(){
return this.city;
}

public void setCity(String newCity){

public class Transaction{

private Trader trader;
private int year;
private int value;

public Transaction(Trader trader, int year, int value)
{
this.trader = trader;
this.year = year;
this.value = value;
}

public Trader getTrader(){
return this.trader;
}

public int getYear(){
return this.year;
}

public int getValue(){
return this.value;
}

public String toString(){
return "{" + this.trader + ", " +
"year: "+this.year+", " +
"value:" + this.value +"}";
}
}

public class PuttingIntoPractice {
public static void main(String... args) {
Trader raoul = new Trader("Raoul", "Cambridge");
Trader mario = new Trader("Mario", "Milan");
Trader alan = new Trader("Alan", "Cambridge");
Trader brian = new Trader("Brian", "Cambridge");

List<Transaction> transactions = Arrays.asList(new Transaction(brian, 2011, 300), new Transaction(raoul, 2012, 1000), new Transaction(raoul, 2011, 400), new Transaction(mario, 2012, 710), new Transaction(mario, 2012, 700), new Transaction(alan, 2012, 950));

// Query 1: Find all transactions from year 2011 and sort them by value (small to high).
List<Transaction> tr2011 = transactions.stream().filter(transaction -> transaction.getYear() == 2011).sorted(comparing(Transaction::getValue)).collect(toList());
System.out.println(tr2011);

// Query 2: What are all the unique cities where the traders work?
List<String> cities = transactions.stream().map(transaction -> transaction.getTrader().getCity()).distinct().collect(toList());
System.out.println(cities);

// Query 3: Find all traders from Cambridge and sort them by name.
List<Trader> traders = transactions.stream().map(Transaction::getTrader).filter(trader -> trader.getCity().equals("Cambridge")).distinct().sorted(comparing(Trader::getName)).collect(toList());
System.out.println(traders);

// Query 4: Return a string of all traders’ names sorted alphabetically.
String traderStr = transactions.stream().map(transaction -> transaction.getTrader().getName()).distinct().sorted().reduce(" ", (n1, n2) -> n1 + n2);
System.out.println(traderStr);

// Query 5: Are there any trader based in Milan?
boolean milanBased = transactions.stream().anyMatch(transaction -> transaction.getTrader().getCity().equals("Milan"));
System.out.println(milanBased);

// Query 6: Update all transactions so that the traders from Milan are set to Cambridge.
transactions.stream().map(Transaction::getTrader).filter(trader -> trader.getCity().equals("Milan")).forEach(trader -> trader.setCity("Cambridge"));
System.out.println(transactions);

// Query 7: What‘s the highest value in all the transactions?
int highestValue = transactions.stream().map(Transaction::getValue).reduce(0, Integer::max);
System.out.println(highestValue);
}
}

Java8實戰Lambda和Stram API學習