chan与sync.WaitGroup实现java中CountDownLatch功能

可以使用chan与sync.WaitGroup实现java中类似CountDownLatch功能。下面分别使用代码示例来说明。

chan的方式如下：

package main

import (
    "time"
    "fmt"
    "io/ioutil"
)

type Job2 struct {
    i    int
    max  int
    text string
}

func outputText2(j *Job2, syn chan int) {
    fileName := j.text + ".txt"
    fileContents := ""

    for j.i < j.max {
        time.Sleep(1 * time.Millisecond)
        fileContents += j.text
        fmt.Println(j.text)
        j.i++
    }

    err := ioutil.WriteFile(fileName, []byte(fileContents), 0644)
    if err != nil {
        panic("something went awry")
    }

    syn <- 1
}

func main() {

    hello := new(Job2)
    hello.text = "hello"
    hello.i = 0
    hello.max = 3

    world := new(Job2)
    world.text = "world"
    world.i = 0
    world.max = 5

    var syn = make(chan int, 2)
    go outputText2(hello, syn)
    go outputText2(world, syn)

    <-syn
    <-syn
    fmt.Println("completed over")
    //可以有2种同步方式，sync.WaitGroup/chan
}

sync.WaitGroup的实现方式如下：

package main

import (
    "time"
    "fmt"
    "io/ioutil"
    "sync"
)

type Job1 struct {
    i    int
    max  int
    text string
}

func outputText1(j *Job1, wg *sync.WaitGroup) {

    defer (*wg).Done()

    fileName := j.text + "1.txt"
    fileContents := ""

    for j.i < j.max {
        time.Sleep(1 * time.Millisecond)
        fileContents += j.text
        fmt.Println(j.text)
        j.i++
    }

    err := ioutil.WriteFile(fileName, []byte(fileContents), 0644)
    if err != nil {
        panic("something went awry")
    }
}

func main() {

    //var wg sync.WaitGroup
    wg := new(sync.WaitGroup)

    hello := new(Job1)
    hello.text = "hello"
    hello.i = 0
    hello.max = 3

    world := new(Job1)
    world.text = "world"
    world.i = 0
    world.max = 5

    go outputText1(hello, wg)
    go outputText1(world, wg)

    wg.Add(2)
    wg.Wait()
    fmt.Println("completed over")
    //可以有2种同步方式，sync.WaitGroup/chan
}