论A+B Problem 的十种解法

//java way 1:use objective Scanner
import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        Scanner scanner=new Scanner(System.in);
        int a=scanner.nextInt();
        int b=scanner.nextInt();
        System.out.println(a+b);
    }
}

//java way 2:use un-objective Scanner
import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        int a= new Scanner(System.in).nextInt();
        int b= new Scanner(System.in).nextInt();
        System.out.println(a+b);
    }
}

//java way 3:use String.split Scanner
import java.util.Arrays;
import java.util.Scanner;
import org.jetbrains.annotations.*;
public class Main
{
    public static int stoi(@NotNull String a)//在洛谷中,禁用@NotNull和对应的import (import org....)
    {
        int ans=0;
        for(int i=0;i<=a.length()-1;i++)
        {
            ans*=10;
            ans+=a.toCharArray()[i]-'0';
        }
        return ans;
    }
    public static void main(String[] args)
    {
        String a=new Scanner(System.in).nextLine();
        String x= a.split(" ")[0];
        int xx=stoi(x);
        String y=a.split(" ")[1];
        int yy=stoi(y);
        System.out.println(xx+yy);
    }
}

//java way 3:use String.split Scanner
import java.util.Arrays;
import java.util.Scanner;
import org.jetbrains.annotations.*;
public class Main
{
    public static int stoi(@NotNull String a)//还是一样
    {
        boolean flag= a.toCharArray()[0] == '-';
        int ans=0;
        int ans_neg=(a.toCharArray()[0]=='-'?-1:1);
        for(int i=(a.toCharArray()[0]=='-'?1:0);i<=a.length()-1;i++)
        {
            ans*=10;
            ans+=a.toCharArray()[i]-'0';
        }
        return ans*ans_neg;
    }
    public static void main(String[] args)
    {
        String a=new Scanner(System.in).nextLine();
        String x= a.split(" ")[0];
        int xx=stoi(x);
        String y=a.split(" ")[1];
        int yy=stoi(y);
        System.out.println(xx+yy);
    }
}