我在计算 a+b 利用 BufferedReader . 我尝试了两种代码，每种都使用 read() 及 readLine() ，但我不明白为什么第一个代码有效，而第二个代码无效。两者之间有什么区别吗 Integer.parseInt(br.readline()) 及 br.read()-'0' ? 它们不是都返回原语int吗？这是第一个代码。它很好用。

package level3;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.util.StringTokenizer;

public class ABPlusFast {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;
        int t = Integer.parseInt(br.readLine());

        for (int i=0; i<t; i++) {
            st = new StringTokenizer(br.readLine());
            int a = Integer.parseInt(st.nextToken());
            int b = Integer.parseInt(st.nextToken());
            bw.write(a+b+"\n");
        }
        bw.flush();
        bw.close();
    }
}

这是第二个不起作用的代码。如果我给一个数字作为输入，那么它返回一个 NoSuchElementException() 在里面 StringTokenizer.class .

package level3;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.IOException;
import java.util.StringTokenizer;

public class ABPlusFast {
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;
        int t = br.read();

        for (int i=0; i<(t-'0'); i++) {
            st = new StringTokenizer(br.readLine());
            int a = Integer.parseInt(st.nextToken());
            int b = Integer.parseInt(st.nextToken());
            bw.write(a+b+"\n");
        }
        bw.flush();
        bw.close();
    }
}