如何从字符串生成流？

import io

string = "Hello, world!"
stream = io.StringIO(string)

import java.io.ByteArrayInputStream;
import java.io.InputStream;

public class Main {
    public static void main(String[] args) {
        String string = "Hello, world!";
        InputStream stream = new ByteArrayInputStream(string.getBytes());
    }
}

const Readable = require('stream').Readable;

const string = 'Hello, world!';
const stream = new Readable();

stream.push(string);
stream.push(null);

using System;
using System.IO;
using System.Text;

class Program
{
    static void Main()
    {
        string text = "Hello, world!";
        byte[] bytes = Encoding.UTF8.GetBytes(text);
        MemoryStream stream = new MemoryStream(bytes);
    }
}