The relationship between Android kotlin coroutines and threads

In app development, the direct switching between the main thread and the time-consuming thread is also a common function, such as switching execution between three UI threads and sub-threads

Case code such as:

package com.study.componentproject

import android.util.Log

class KotlinUtil {
   
    
    
    private var TAG ="Util"
    fun ioThread_1() {
   
    
    
        Log.e(TAG,"IO线程1==${Thread.currentThread().name}")
    }

    fun ioThread_2() {
   
    
    
        Log.e