10月16 JDK1.8新特性函数式编程

public static void main(String[] args) {
        
        List<String> alpha = Arrays.asList("a","b","c");
    
        List<String> collect = alpha.stream().map(String::toUpperCase).collect(Collectors.toList());
        for (String str : collect) {
            System.out.println(str);
        }
        // A    B    C
        
        List<Integer> num = Arrays.asList(2,4,5);
        List<Integer> coll1 = num.stream().map(n -> n*2).collect(Collectors.toList());
        for (Integer i : coll1) {
            System.out.println(i);
        }
        // 4 8 10
        //1. 查询所有在架的商品
        List<ProductInfo> productInfoList = new ArrayList<>();
        ProductInfo info1 = new ProductInfo();
        info1.setCategoryType(1);
        info1.setProductName("name1");
        
        ProductInfo info2 = new ProductInfo();
        info2.setCategoryType(1);
        info2.setProductName("name2");
        
        ProductInfo info3 = new ProductInfo();
        info3.setCategoryType(2);
        info3.setProductName("name3");
        
        productInfoList.add(info1);
        productInfoList.add(info2);
        productInfoList.add(info3);
        //2. 获取类目type列表
        List<Integer> categoryTypeList = productInfoList.stream()
                .map(ProductInfo::getCategoryType)
                .collect(Collectors.toList());
        for (Integer integer : categoryTypeList) {
            System.out.println(integer);
        }
        // 1 1 2 就是将type 放到集合里
    }