Could not resolve host: libraries.minecraft.net

I'm getting this error while trying to install any Minecraft version

Failed to download file. Name: netty-1.8.8.jar URL: https://libraries.minecraft.net/com/mojang/netty/1.8.8/netty-1.8.8.jar Error details: Could not resolve host: libraries.minecraft.net Filename on disk: netty-1.8.8.jar Path: C:\Users\Usuario\AppData\Roaming\.minecraft\libraries\com\mojang\netty\1.8.8\netty-1.8.8.jar Exists: Nonexistent

and sometimes i'm getting this error too:

Unable to locate the Java runtime.
Error details: 0x00000000 - system: A opera磯 foi conclu� com 긩to.
Filename on disk: javaw.exe
Path: C:\Users\Usuario\AppData\Local\Packages\Microsoft.4297127D64EC6_8wekyb3d8bbwe\LocalCache\Local\runtime\jre-legacy\windows-x64\jre-legacy\bin\javaw.exe
Exists: Nonexistent

 but i have the jre 1.8 installed on my computer.

waiting for help.