Okay i found my problem.
See the " at the start and end from token, and baerer?
The problem was, that was a part from this string. I fixt id 
Just replace every " with nothing
Updatet java object:
package de.minetrain.kekbot.discord.features.live_notification.obj;
import com.google.gson.JsonObject;
/**
* This class represents a Twitch access token, which is used to authorize requests to the Twitch API.
* @author MineTrain/Justin
* @since 29.01.2023
* @version 1.1
*/
public class TwitchAccesToken {
private final int expiresIn; //The number of milliseconds until the access token expires.
private final String accessToken; //The actual access token value.
private final String tokenType; //The token type, which should always "bearer" for Twitch access tokens.
/**
* Constructs a new TwitchAccessToken object from a JSON object.
* @param json The JSON object containing the access token data.
*/
public TwitchAccesToken(JsonObject json) {
this.expiresIn = Integer.parseInt(String.valueOf(json.get("expires_in")).replace("\"", ""));
this.accessToken = String.valueOf(json.get("access_token")).replace("\"", "");
this.tokenType = String.valueOf(json.get("token_type")).replace("\"", "");
System.out.println(accessToken+", "+tokenType+", "+expiresIn);
}
/**
* Check if the token is expired
* @return true if expiresIn < 5 else false
*/
public boolean isExpired(){
return (expiresIn>5) ? false:true;
}
/**
* @return The number of seconds until the access token expires.
*/
public int getExpiresIn() {
return expiresIn;
}
/**
* @return The actual access token value.
*/
public String getAccessToken() {
return accessToken;
}
/**
* @return The token type, which is always "bearer" for Twitch access tokens.
*/
public String getTokenType() {
return tokenType;
}
@Override
public String toString() {
return accessToken;
}
}
Sry for this unnecessary post ;D