java lambda循环_使用Java 8 Lambda简化嵌套循环操作

float[][] values = ...
for (int i = 0; i < values.length; i++) {
 for (int k = 0; k < values[i].length; k++) {
 float value = values[i][k];
 // do something with i, k and value
 }
}

private void loop(float[][] values, BiConsumer<Integer, Integer> consumer) {
 for (int i = 0; i < values.length; i++) {
 for (int k = 0; k < values[i].length; k++) {
 consumer.accept(i, k);
 }
 }
}

float[][] values = ...
loop(values, (i, k) -> {
 float value = values[i][k];
 // do something with i, k and value
});

@Test
 public void test() {
 
 // 数据并行化处理
 // 学生集合
 Person kobe = new Person("kobe", 40, 1);
 Person jordan = new Person("jordan", 50, 1);
 Person mess = new Person("mess", 20, 2);
 List<Person> personList = Arrays.asList(kobe, jordan, mess);
 
 long beginTime = System.currentTimeMillis();
 
 // 原来的方式
 List<Person> oldBoys = new ArrayList<>(personList.size());
 for (Person p : personList) {
  // 性别男
  if (p.getSex() == 1) {
  oldBoys.add(p);
  }
 }
 long endTime = System.currentTimeMillis();
 log.info("原来的方式 take time:" + (endTime - beginTime));
 
 beginTime = System.currentTimeMillis();
 // 流方式：找出所有男同学
 List<Person> newBoys = personList.stream()
 .filter(p -> 1 == p.getSex())
 .collect(Collectors.toList());
 
 endTime = System.currentTimeMillis();
 log.info("流方式 take time:" + (endTime - beginTime));
 
 
 beginTime = System.currentTimeMillis();
 // 流方式：找出所有男同学
 List<Person> parallelBoys = personList.parallelStream()
 .filter(p -> 1 == p.getSex())
 .collect(Collectors.toList());
 
 endTime = System.currentTimeMillis();
 log.info("并行流方式 take time:" + (endTime - beginTime));
 }

@Test
	public void test() {
 
		// 学生集合
		List<Person> personList = new ArrayList<>(1000000);
		for (int i = 0, j = 1000000; i < j; i++) {
			int sex = i % 2;
			Person p = new Person(String.valueOf(i), i, sex);
			personList.add(p);
		}
 
		long beginTime2 = System.currentTimeMillis();
		// 流方式：年龄之和
		int parallelAges = personList.parallelStream().mapToInt(p -> p.getAge()).sum();
 
		long endTime2 = System.currentTimeMillis();
		log.info("并行流方式 take time:" + (endTime2 - beginTime2));
		log.info("parallelAges:" + parallelAges);
 
		long beginTime = System.currentTimeMillis();
 
		// 原来的方式
		int totalAge = 0;
		for (Person p : personList) {
			// 年龄之和
			totalAge = totalAge + p.getAge();
		}
		long endTime = System.currentTimeMillis();
		log.info("原来的方式 take time:" + (endTime - beginTime));
		log.info("totalAge:" + totalAge);
 
	}