03-jdk8中间操作

心已赠人 2023-10-11 14:59 5阅读 0赞

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hhY2NwSjJFRQ_size_16_color_FFFFFF_t_70][]

public class Employee {
    
        private Integer salary;
    
        private String name;
    
        public Employee(String name,Integer salary) {
            this.salary = salary;
            this.name = name;
        }
    
        public Integer getSalary() {
            return salary;
        }
    
        public void setSalary(Integer salary) {
            this.salary = salary;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public Employee(String name) {
            this.name = name;
        }
    
        public Employee() {
            this.name = name;
        }
    
        @Override
        public String toString() {
            return "Employee{" +
                    "salary=" + salary +
                    ", name='" + name + '\'' +
                    '}';
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            Employee employee = (Employee) o;
            return Objects.equals(salary, employee.salary) &&
                    Objects.equals(name, employee.name);
        }
    
        @Override
        public int hashCode() {
            return Objects.hash(salary, name);
        }
    }

public class Demo6 {
    
            public static void main(String[] args) {
                ArrayList<Employee> lst=new ArrayList<>();
                lst.add(new Employee("小王",1000));
                lst.add(new Employee("小张",11000));
                lst.add(new Employee("小刘",11000));
                lst.add(new Employee("小孙",14000));
                lst.add(new Employee("小李",15000));
                lst.add(new Employee("小李",15000));
    
                //中间操作
                //1、filter过滤
                System.out.println("--filter过滤------------------------------------------");
                lst.stream()
                        .filter(e -> e.getSalary() > 10000)
                        .forEach(System.out::println);
                //2、limit 限制
                System.out.println("--limit 限制------------------------------------------");
                lst.stream()
                        .limit(2)
                        .forEach(System.out::println);
                //3、skip 跳过
                System.out.println("--skip 跳过------------------------------------------");
                lst.stream()
                        .skip(2)
                        .forEach(System.out::println);
    
                //4、distinct 去掉重复]
                System.out.println("---distinct 去掉重复-----------------------------------------");
                lst.stream().distinct().forEach(System.out::println);
    
    
                //5、sorted 排序
                System.out.println("--sorted 排序------------------------------------------");
                lst.stream().sorted((e1,e2)->Integer.compare(e1.getSalary(),e2.getSalary()))
                        .forEach(System.out::println);
    
    
                //中间操作2 map
                System.out.println("--中间操作2 map------------------------------------------");
                lst.stream().map(e->e.getName()).forEach(System.out::println);//获取姓名
    
    
                //中间操作3 parallel 并行流，采用多线程 效率高
                System.out.println("--中间操作3 parallel-----------------------------------------");
                lst.parallelStream().forEach(System.out::println);
            }

执行结果：

--filter过滤------------------------------------------
    Employee{salary=11000, name='小张'}
    Employee{salary=11000, name='小刘'}
    Employee{salary=14000, name='小孙'}
    Employee{salary=15000, name='小李'}
    Employee{salary=15000, name='小李'}
    --limit 限制------------------------------------------
    Employee{salary=1000, name='小王'}
    Employee{salary=11000, name='小张'}
    --skip 跳过------------------------------------------
    Employee{salary=11000, name='小刘'}
    Employee{salary=14000, name='小孙'}
    Employee{salary=15000, name='小李'}
    Employee{salary=15000, name='小李'}
    ---distinct 去掉重复-----------------------------------------
    Employee{salary=1000, name='小王'}
    Employee{salary=11000, name='小张'}
    Employee{salary=11000, name='小刘'}
    Employee{salary=14000, name='小孙'}
    Employee{salary=15000, name='小李'}
    --sorted 排序------------------------------------------
    Employee{salary=1000, name='小王'}
    Employee{salary=11000, name='小张'}
    Employee{salary=11000, name='小刘'}
    Employee{salary=14000, name='小孙'}
    Employee{salary=15000, name='小李'}
    Employee{salary=15000, name='小李'}
    --中间操作2 map------------------------------------------
    小王
    小张
    小刘
    小孙
    小李
    小李
    --中间操作3 parallel-----------------------------------------
    Employee{salary=14000, name='小孙'}
    Employee{salary=15000, name='小李'}
    Employee{salary=15000, name='小李'}
    Employee{salary=11000, name='小张'}
    Employee{salary=11000, name='小刘'}
    Employee{salary=1000, name='小王'}

多线程执行效率

public class Demo7 {
    
        public static void main(String[] args) {
            //串行流 和并行流的区别
            ArrayList<String> list=new ArrayList<>();
            for(int i=0;i<5000000;i++){
                list.add(UUID.randomUUID().toString());
            }
    
            //串行
            long time=System.currentTimeMillis();
    //        long count = list.stream().sorted().count();
    //        System.out.println(count);
    //        System.out.println("用时："+(System.currentTimeMillis()-time));
    
            time=System.currentTimeMillis();
            long count1 = list.parallelStream().sorted().count();
            System.out.println(count1);
            System.out.println("用时："+(System.currentTimeMillis()-time));
        }
    }

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