1、map的基本用法

package main;

import "fmt";

func main() {
    var map1 map[string]int;
    map2 := make(map[string]int);
    var map3 map[string]int;

    map1 = map[string]int{"key1": 1, "key2": 2};
    map3 = map1;

    map2["k1"] = 11;

    fmt.Printf("map1: %d\n", map1["key1"]);
    fmt.Printf("map2: %d\n", map2["k1"]);
    fmt.Printf("map3: %d\n", map3["key1"]);

    // map3直接指向map1， 所以会修改原来的map1
    map3["key1"] = 111;
    fmt.Printf("map1: %d\n", map1["key1"]);
    fmt.Printf("map3: %d\n", map3["key1"]);
}

2、判断key不存在，还是key的value是空

package main;

import "fmt";

func main() {
    map1 := map[string]string{"key1": "value1", "key2": "value1", "key3": "value3"};

    // key1存在
    _, b1 := map1["key1"];
    fmt.Printf("b1=%t\n", b1);

    // 删除key1
    delete(map1, "key1");

    // key1不存在
    _, b2 := map1["key1"];
    fmt.Printf("b2=%t\n", b2);

}

3、遍历和排序

package main;

import "fmt";
import "sort";

func main() {
    map1 := map[string]string{"key1": "value1", "key2": "value2", "key3": "value3"};

    var keys []string;

    // 注意： go的map对key和value是无序的
    // k和v
    for k, v := range map1 {
        fmt.Printf("k=%s, v=%s\n", k, v);
    }

    // 只取key
    for k := range map1 {
        keys = append(keys, k);
        fmt.Printf("origin map sort, k=%s\n", k);
    }

    // 只取key
    for _, v := range map1 {
        fmt.Printf("v=%s\n", v);
    }

    // 如果一定要排序， 需要将key放到切片中再排序
    sort.Strings(keys);
    for _, k := range keys {
        fmt.Printf("after sort k=%s\n", k);
    }
}