我们正在执行以下编程练习:Death by Coffee。
主要任务是将整数转换为十六进制并添加值。我们编写了以下代码:
public class Dinglemouse {
public static int[] coffeeLimits /*☕*/ (final int year, final int month, final int day) {
System.out.println("year: "+year);
System.out.println("month: "+month);
System.out.println("day: "+day);
long healthNumber = Long.parseLong(String.valueOf(year)+String.valueOf(month)+String.valueOf(day));
System.out.println("healthNumber: "+healthNumber);
long cafe = Long.valueOf("CAFE",16);
long decaf = Long.valueOf("DECAF",16);
int cafeLimit = getLimit(cafe, healthNumber);
System.out.println("\ncafeLimit: "+cafeLimit);
int decafLimit = getLimit(decaf, healthNumber);
System.out.println("\ndecafLimit: "+decafLimit);
return new int []{cafeLimit, decafLimit};
}
public static int getLimit(long coffee, long healthNumber){
int limit=0;
while(limit<=5000 && !Long.toHexString(healthNumber).contains("dead")){
limit++;
healthNumber+=coffee;
System.out.println("new healthNumber: "+Long.toHexString(healthNumber));
}
return limit>5000 ? 0 : limit;
}
}
我们想知道为什么代码通过了除exJohn之外的以下测试:
import org.junit.Test;
import static org.junit.Assert.*;
import java.util.*;
public class Tests {
// Show returned limits
private static int[] show(final int y, final int m, final int d, final int[] result) {
System.out.println(String.format("%4d%02d%02d -> ",y,m,d)+Arrays.toString(result));
return result;
}
@Test
public void exJohn() {
final int y=1950, m=1, d=19;
assertArrayEquals(new int[]{2645,1162}, show(y,m,d,Dinglemouse.coffeeLimits(y,m,d)));
}
@Test
public void exSusan() {
final int y=1965, m=12, d=11;
assertArrayEquals(new int[]{111,0}, show(y,m,d,Dinglemouse.coffeeLimits(y,m,d)));
}
@Test
public void exElizabeth() {
final int y=1964, m=11, d=28;
assertArrayEquals(new int[]{0,11}, show(y,m,d,Dinglemouse.coffeeLimits(y,m,d)));
}
@Test
public void exPeter() {
final int y=1965, m=9, d=4;
assertArrayEquals(new int[]{0,0}, show(y,m,d,Dinglemouse.coffeeLimits(y,m,d)));
}
}
我们已经打印了在getLimit循环中得到的内容,我们看到为咖啡店限制输出的最后一个healthNumber是:
...
new healthNumber: 2dc4cbb
new healthNumber: 2dd17b9
new healthNumber: 2dde2b7
new healthNumber: 2deadb5
cafeLimit: 889
对于无咖啡因的限量,我们有:
...
new healthNumber: 10ff8a241
new healthNumber: 110068ef0
new healthNumber: 110147b9f
new healthNumber: 11022684e
decafLimit: 0
因此,我们的代码的结果是:[889,0]
何时应该:[2645,1162]
我们认为这可能是由int溢出引起的,所以我们将所有变量都更改为long,但是程序的行为相同。
我们已阅读:
您的代码行
long healthNumber = Long.parseLong(String.valueOf(year)+String.valueOf(month)+String.valueOf(day));
“吃”在日和月中的前导零,您可以将其替换为诸如]
long healthNumber = year*10000+month*100+day;
使其按预期工作。