STREAM APIを使ってみた

anyMatch：判定（一部合致）

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("B");
        bean2.setName("商品B");
        bean2.setNum(100);
        list.add(bean2);

実行

        list.stream().anyMatch(b->b.getCd().equals("A"));//true
        list.stream().anyMatch(b->b.getCd().equals("C"));//false

allMatch： 判定（全て合致）

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("A");
        bean2.setName("商品A");
        bean2.setNum(100);
        list.add(bean2);

実行

        list.stream().allMatch(b->b.getCd().equals("A"));//true
        list.stream().allMatch(b->b.getCd().equals("B"));//false

noneMatch：判定（全て非合致）

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("A");
        bean2.setName("商品A");
        bean2.setNum(100);
        list.add(bean2);

実行

        list.stream().noneMatch(b->b.getCd().equals("A"));//false
        list.stream().noneMatch(b->b.getCd().equals("B"));//true

max：最大値を返す

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("C");
        bean2.setName("商品C");
        bean2.setNum(200);
        list.add(bean2);

実行

        list.stream().map(b->b.getNum()).max(Comparator.naturalOrder()).get();//200

findAny：任意の値を返す

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("C");
        bean2.setName("商品C");
        bean2.setNum(200);
        list.add(bean2);

実行

        list.stream().findAny().map(b->b.getCd()).orElse(null);//A

findFirst：先頭の値を返す

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("C");
        bean2.setName("商品C");
        bean2.setNum(200);
        list.add(bean2);

実行

        list.stream().findFirst().map(b->b.getCd()).orElse(null);//A

sum：合計を返す

セット

        List<TestBean> list = new ArrayList<>();
        TestBean bean1 = new TestBean();
        bean1.setCd("A");
        bean1.setName("商品A");
        bean1.setNum(100);
        list.add(bean1);
        TestBean bean2 = new TestBean();
        bean2.setCd("B");
        bean2.setName("商品B");
        bean2.setNum(100);
        list.add(bean2);
        TestBean bean3 = new TestBean();
        bean3.setCd("A");
        bean3.setName("商品A");
        bean3.setNum(100);
        list.add(bean3);

実行

        list.stream().filter(b->b.getCd().equals("A")).mapToInt(b->b.getNum()).sum();//200