格林模拟试题三参考答案

Answers

Answer to Question 1)

1) float f=1/3;

2) int i=1/3;

4) double d=999d;

The fact that option 3 does not compile may be a surprise. The problem is because the default type for a number with a decimal component is a double and not a float. The additional trailing d in the option with 999 doesn't help, but it doesn't harm.

Answer to Question 2)

2) new

The option NULL (note the upper case letter) is definitely not a keyword. There is some discussion as to i. There is some discussion as to if null is a keyword but for the purpose of the exam you should probably assume it is a keyword.

The option instanceOf is a bit of a misleading option that would probably not occur on the exam. The real keyword is instanceof (note that the of has no capital letter O). I had the incorrect version in an earlier version of this tutorial as it looks more likely to my eyes. The instanceof keyword looks like a method, but it is actually an operator.

The option wend is probably valid in some other language to indicate the end of a while loop, but Java has no such keyword.

Answer to Question 3)

1) System.out.println(1+1);

2) int i=2+'2';

Option 3 is not valid because single quotes are used to indicate a character constant and not a string. Several people have emailed me to say that option 3 will compile. When they eventually compiled the exact code they have agreed, it will not compile. Let me re-state that

String s="on"+'one';