JAVA 8 Stream 自查自用

 //dm
    @Data
    private static class Cat {
        private String name ;
        private BigDecimal price;
        private int age;
    }

    /**
     * 属性求和
     */
    @Test
    public  void testSum(){
        Cat cat = new Cat();
        cat.setAge(1);
        cat.setName("tudou");
        cat.setPrice(new BigDecimal(1));
        Cat cat2 = new Cat();
        cat2.setAge(1);
        cat2.setName("tudou2");
        cat2.setPrice(new BigDecimal(1));
        final List<Cat> cats = Arrays.asList(cat, cat2);
        final Integer reduce = cats.stream().reduce(0, (temp, y) -> temp + y.getAge(), Integer::sum);
        Assert.isTrue(reduce==2);
    }

    /**
     * 属性相乘求和
     */
    @Test
    public void testSumMultiple() {
        Cat cat = new Cat();
        cat.setAge(1);
        cat.setName("tudou");
        cat.setPrice(new BigDecimal(1));
        Cat cat2 = new Cat();
        cat2.setAge(1);
        cat2.setName("tudou2");
        cat2.setPrice(new BigDecimal(1));
        final List<Cat> cats = Arrays.asList(cat, cat2);
        final BigDecimal reduce = cats.stream().reduce(BigDecimal
                .ZERO, (temp, y) -> temp.add(new BigDecimal(y.getAge()).multiply(y.getPrice())), BigDecimal::add);
        Assert.isTrue(reduce.equals(new BigDecimal(3)));
    }

参考文章 https://www.baeldung.com/java-stream-reduce