Lambda性能

• 排序:单CPU环境下lambda排序比Collections提供的排序方法慢

  public class Appliction {
    public static void main(String[] args) {
        Random random = new Random();
        List<Integer> list = Lists.newArrayList();
        for (int i = 0; i < 2000000; i++) {
            list.add(random.nextInt());
        }
  
        long beginTime = System.currentTimeMillis();
        List<Integer> collect = list.stream().sorted((a, b) -> a.compareTo(b)).collect(Collectors.toList());
        System.err.println(System.currentTimeMillis() - beginTime);
  
        long c2 = System.currentTimeMillis();
        Collections.sort(list);
        System.err.println(System.currentTimeMillis() - c2);
    }
  
    private static Integer max(List<Integer> list) {
        Integer min = Integer.MIN_VALUE;
        for (Integer i : list) {
            min = Integer.max(i, min);
        }
        return min;
    }
  }
  out =====>
  1025 // lamdba排序
  759
  

• 查找

  public class Appliction {
    public static void main(String[] args) {
        Random random = new Random();
        List<Integer> list = Lists.newArrayList();
        for (int i = 0; i < 2000000; i++) {
            list.add(random.nextInt());
        }
  
        long beginTime = System.currentTimeMillis();
        Integer max = list.stream().max((a, b) -> a.compareTo(b)).get();
        System.err.println(System.currentTimeMillis() - beginTime);
        System.err.println(max);
  
        long c2 = System.currentTimeMillis();
        Integer max2 = max(list);
        System.err.println(System.currentTimeMillis() - c2);
        System.err.println(max2);
    }
  
    private static Integer max(List<Integer> list) {
        Integer min = Integer.MIN_VALUE;
        for (Integer i : list) {
            min = Integer.max(i, min);
        }
        return min;
    }
  }
  out =====>
  116        // lambda查找
  2147472958
  23
  2147472958