Java源码-断言（Assertion）初接触

学Java这么久，第一次调试断言。

收获：

1.在命令行中调试断言：使用 java -ea AssertTest的方式（刚开始没带-ea参数，以为程序有问题呢）

2.在Eclipse中调试断言：run as configuration->Arguments->VM arguments->输入“-ea”->run（相比之下，命令行下调试更方便一点）

代码：

package example;

//Fig. 11.8: AssertTest.java
//Checking with assert that a value is within range.
import java.util.Scanner;

public class AssertTest
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);

System.out.print("Enter a number between 0 and 10: ");
int number = input.nextInt();

// assert that the value is >= 0 and <= 10
assert (number >= 0 && number <= 10) : "bad number: " + number;

System.out.printf("You entered %d%n", number);
}
} // end class AssertTest

运行结果：
1. Round 1
Enter a number between 0 and 10: 11

Exception in thread "main" java.lang.AssertionError: bad number: 11

 at example.AssertTest.main(AssertTest.java:17)

2. Round 2
Enter a number between 0 and 10: 10

You entered 10