Jdk9快速创建只读集合

• jdk9之前创建只读集合

public class Main {
    
    public static void main(String[] args)throws Exception  {
        List<String> list = new ArrayList<>();
        list.add("SpringBoot课程");
        list.add("架构课程");
        list.add("微服务SpringCloud课程");
        //设置为只读List集合
        list = Collections.unmodifiableList(list);
        System.out.println(list);
 
        Set<String> set = new HashSet<>();
        set.add("Mysql教程");
        set.add("Linux服务器教程");
        set.add("Git教程");
        //设置为只读Set集合
        set = Collections.unmodifiableSet(set);
        System.out.println(set);
 
        Map<String, String> map = new HashMap<>();
        map.put("key1", "课程1");
        map.put("key2", "课程2");
        //设置为只读Map集合
        map = Collections.unmodifiableMap(map);
        System.out.println(map);
    }
    
}

• 使用jdk9创建只读集合

public class Main {
 
    public static void main(String[] args)throws Exception  {
        List<String> list = List.of("SpringBoot教程","架构课程","微服务SpringCloud课程");
        System.out.println(list);
 
        Set<String> set = Set.of("Mysql课程","Linux服务器教程","Git教程");
        System.out.println(set);
 
        Map<String, String> map = Map.of("key1","课程1","key2","课程2");
        System.out.println(map);
    }
 
}