>>150
そんなめんどくさい方法思いつく方が難しいって。
乱数作ってやる方が一般的でしょう。

// MultiplicationDemo.java
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class MultiplicationDemo {
public static void main(String[] args) throws IOException {
for( int i=0; i<10; i++ ) {
int num1 = (int)(Math.random() * 9) + 1;
int num2 = (int)(Math.random() * 9) + 1;
System.out.println( "(" + (i+1) + ") " + num1 + "×" + num2 + "＝？" );
BufferedReader br = new BufferedReader( new InputStreamReader(System.in) );
int paper = 0;
try {
paper = Integer.parseInt( br.readLine() );
if( paper == num1 * num2 ) System.out.println( "正解!!" );
else System.out.println( "不正解..." );
} catch(NumberFormatException nfe) {
System.out.println( "入力ミス..." );
}
}
}
}