Rojer.2019.01.31

今天發現到 JAVA 的 Predicate 用法，感覺規則比較複雜的時候，可以用這樣的方式來簡化一下程式碼，下面是使用的範例。

資料格式

public class Item {

public String ItemName;

public String ItemNo;

public String ItemSource;

public Integer Total;

public Item(String itemName, String itemNo, String itemSource, Integer total) {

ItemName = itemName;

ItemNo = itemNo;

ItemSource = itemSource;

Total = total;

}

}

public class Main {

public static void main(String[] args) {

Predicate<Item> rule1 = x -> x.ItemName.equals("Name1");

List<Item> list = new ArrayList<Item>();

Item it = new Item("Name2", "No2", "E", 25);

list.add(it);

it = new Item("Name2", "No1", "D", 20);

list.add(it);

it = new Item("Name1", "No2", "C", 15);

list.add(it);

it = new Item("Name1", "No1", "B", 5);

list.add(it);

it = new Item("Name1", "No1", "A", 10);

list.add(it);

long x1 = list.stream().filter(x -> 

x.ItemName.equals("Name1")).count();

long x2 = list.stream().filter(rule1).count();


//x1 x2 結果相同



System.out.println("x1=" + x1);

System.out.println("x2=" + x2);

}

}