1、先转成String 2、截取处理

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        double d = scanner.nextDouble();
        System.out.println(Main.typeConversion(d));
    }
    public static int typeConversion(double d){

        String doubleString = String.valueOf(d);
        String subStr = doubleString.substring(0, doubleString.indexOf("."));
        return Integer.parseInt(subStr);
        

    }
}