java8 Stream 的操作步骤3 终止操作

public class TestStreamAPI2 {
 
 List<Employee> emps = Arrays.asList(
   new Employee(102, "李四", 59, 6666.66, Status.BUSY),
   new Employee(101, "张三", 18, 9999.99, Status.FREE),
   new Employee(103, "王五", 28, 3333.33, Status.VOCATION),
   new Employee(104, "赵六", 8, 7777.77, Status.BUSY),
   new Employee(104, "赵六", 8, 7777.77, Status.FREE),
   new Employee(104, "赵六", 8, 7777.77, Status.FREE),
   new Employee(105, "田七", 38, 5555.55, Status.BUSY)
 );
 
 //3. 终止操作
 /*
  allMatch——检查是否匹配所有元素
  anyMatch——检查是否至少匹配一个元素
  noneMatch——检查是否没有匹配的元素
  findFirst——返回第一个元素
  findAny——返回当前流中的任意元素
  count——返回流中元素的总个数
  max——返回流中最大值
  min——返回流中最小值
  */
 @Test
 public void test1(){
   boolean bl = emps.stream()
    .allMatch((e) -> e.getStatus().equals(Status.BUSY));
   
   System.out.println(bl);
   
   boolean bl1 = emps.stream()
    .anyMatch((e) -> e.getStatus().equals(Status.BUSY));
   
   System.out.println(bl1);
   
   boolean bl2 = emps.stream()
    .noneMatch((e) -> e.getStatus().equals(Status.BUSY));
   
   System.out.println(bl2);
 }
 
 @Test
 public void test2(){
  Optional<Employee> op = emps.stream()
   .sorted((e1, e2) -> Double.compare(e1.getSalary(), e2.getSalary()))
   .findFirst();
  
  System.out.println(op.get());
  
  System.out.println("--------------------------------");
  
  Optional<Employee> op2 = emps.parallelStream()
   .filter((e) -> e.getStatus().equals(Status.FREE))
   .findAny();
  
  System.out.println(op2.get());
 }
 
 @Test
 public void test3(){
  long count = emps.stream()
       .filter((e) -> e.getStatus().equals(Status.FREE))
       .count();
  
  System.out.println(count);
  
  Optional<Double> op = emps.stream()
   .map(Employee::getSalary)
   .max(Double::compare);
  
  System.out.println(op.get());
  
  Optional<Employee> op2 = emps.stream()
   .min((e1, e2) -> Double.compare(e1.getSalary(), e2.getSalary()));
  
  System.out.println(op2.get());
 }
 
 //注意：流进行了终止操作后，不能再次使用
 @Test
 public void test4(){
  Stream<Employee> stream = emps.stream()
   .filter((e) -> e.getStatus().equals(Status.FREE));
  
  long count = stream.count();
  
  stream.map(Employee::getSalary)
   .max(Double::compare);
 }
} 

public class TestStreamAPI3 {
 
 List<Employee> emps = Arrays.asList(
   new Employee(102, "李四", 79, 6666.66, Status.BUSY),
   new Employee(101, "张三", 18, 9999.99, Status.FREE),
   new Employee(103, "王五", 28, 3333.33, Status.VOCATION),
   new Employee(104, "赵六", 8, 7777.77, Status.BUSY),
   new Employee(104, "赵六", 8, 7777.77, Status.FREE),
   new Employee(104, "赵六", 8, 7777.77, Status.FREE),
   new Employee(105, "田七", 38, 5555.55, Status.BUSY)
 );
 
 //3. 终止操作
 /*
  归约
  reduce(T identity, BinaryOperator) / reduce(BinaryOperator) ——可以将流中元素反复结合起来，得到一个值。
  */
 @Test
 public void test1(){
  List<Integer> list = Arrays.asList(1,2,3,4,5,6,7,8,9,10);
  
  Integer sum = list.stream()
   .reduce(0, (x, y) -> x + y);
  
  System.out.println(sum);
  
  System.out.println("----------------------------------------");
  
  Optional<Double> op = emps.stream()
   .map(Employee::getSalary)
   .reduce(Double::sum);
  
  System.out.println(op.get());
 }
 
 //需求：搜索名字中 “六” 出现的次数
 @Test
 public void test2(){
  Optional<Integer> sum = emps.stream()
   .map(Employee::getName)
   .flatMap(TestStreamAPI1::filterCharacter)
   .map((ch) -> {
    if(ch.equals('六'))
     return 1;
    else 
     return 0;
   }).reduce(Integer::sum);
  
  System.out.println(sum.get());
 }
 
 //collect——将流转换为其他形式。接收一个 Collector接口的实现，用于给Stream中元素做汇总的方法
 @Test
 public void test3(){
  List<String> list = emps.stream()
   .map(Employee::getName)
   .collect(Collectors.toList());
  
  list.forEach(System.out::println);
  
  System.out.println("----------------------------------");
  
  Set<String> set = emps.stream()
   .map(Employee::getName)
   .collect(Collectors.toSet());
  
  set.forEach(System.out::println);

  System.out.println("----------------------------------");
  
  HashSet<String> hs = emps.stream()
   .map(Employee::getName)
   .collect(Collectors.toCollection(HashSet::new));
  
  hs.forEach(System.out::println);
 }
 
 @Test
 public void test4(){
  Optional<Double> max = emps.stream()
   .map(Employee::getSalary)
   .collect(Collectors.maxBy(Double::compare));
  
  System.out.println(max.get());
  
  Optional<Employee> op = emps.stream()
   .collect(Collectors.minBy((e1, e2) -> Double.compare(e1.getSalary(), e2.getSalary())));
  
  System.out.println(op.get());
  
  Double sum = emps.stream()
   .collect(Collectors.summingDouble(Employee::getSalary));
  
  System.out.println(sum);
  
  Double avg = emps.stream()
   .collect(Collectors.averagingDouble(Employee::getSalary));
  
  System.out.println(avg);
  
  Long count = emps.stream()
   .collect(Collectors.counting());
  
  System.out.println(count);
  
  System.out.println("--------------------------------------------");
  
  DoubleSummaryStatistics dss = emps.stream()
   .collect(Collectors.summarizingDouble(Employee::getSalary));
  
  System.out.println(dss.getMax());
 }
 
 //分组
 @Test
 public void test5(){
  Map<Status, List<Employee>> map = emps.stream()
   .collect(Collectors.groupingBy(Employee::getStatus));
  
  System.out.println(map);
 }
 
 //多级分组
 @Test
 public void test6(){
  Map<Status, Map<String, List<Employee>>> map = emps.stream()
   .collect(Collectors.groupingBy(Employee::getStatus, Collectors.groupingBy((e) -> {
    if(e.getAge() >= 60)
     return "老年";
    else if(e.getAge() >= 35)
     return "中年";
    else
     return "成年";
   })));
  
  System.out.println(map);
 }
 
 //分区
 @Test
 public void test7(){
  Map<Boolean, List<Employee>> map = emps.stream()
   .collect(Collectors.partitioningBy((e) -> e.getSalary() >= 5000));
  
  System.out.println(map);
 }
 
 //
 @Test
 public void test8(){
  String str = emps.stream()
   .map(Employee::getName)
   .collect(Collectors.joining("," , "----", "----"));
  
  System.out.println(str);
 }
 
 @Test
 public void test9(){
  Optional<Double> sum = emps.stream()
   .map(Employee::getSalary)
   .collect(Collectors.reducing(Double::sum));
  
  System.out.println(sum.get());
 }
}