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练习题

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追风少年

#1 Created at ... [Delete] [Delete and Lock User] 
Scanner scanner = new Scanner(System.in);
System.out.print("请输入上次考试的成绩：");
int scorePre = scanner.nextInt();
System.out.print("请输入本次考试的成绩：");
int scoreNow = scanner.nextInt();
float per = (float)(scoreNow - scorePre) / scorePre * 100;
System.out.printf("您的成绩提高了：%.2f%%\n", per);

风

#2 Created at ... [Delete] [Delete and Lock User] 
(float)(scoreNow - scorePre) / scorePre * 100;

为啥前面要加（float）

Healer.

#3 Created at ... [Delete] [Delete and Lock User] 
(float)(scoreNow - scorePre) / scorePre * 100;

整数减整数得整数，整数除以整数 scorePre，结果仍然是整数。最后，整数结果再乘以 100，得到的仍然是整数。如果希望得到一个浮点数结果，就需要在 (scoreNow - scorePre) 表达式前面加上 (float) 进行类型转换，将整数除法的结果转换为浮点数，从而得到期望的浮点数结果。

就不告诉你

#4 Created at ... [Delete] [Delete and Lock User] 
%.2f本身就是格式化浮点数，不用加（float）也是一样的结果

就不告诉你

#5 Created at ... [Delete] [Delete and Lock User]

是需要加(float)的，我以为不用。。。

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