Working with Java Streams Processing-03

Let's look at some of the stream operations closely with the help of the examples. Let's build the domain object first.

Traders and Transactions:

public class Trader{
    private final String name;
    private final 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 String toString(){
        return "Trader:"+this.name + " in " + this.city;
    }
}
public class Transaction{
    private final Trader trader;
    private final int year;
    private final 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 +"}";
    }
}

Creating Traders and Transactions.

Trader raoul = new Trader("Raoul", "Cambridge");
Trader mario = new Trader("Mario","Milan");
Trader alan = new…