int类型的意外输出

Question

学习JAVA,我试图测试while循环的上限继续增加int.请参阅下面的程序:

 public class Test {

   public static int a(){
     int a = 10;
      while(a > 9 )
          ++a;
      return a; 
   }

   public static void main(String[] argc) {

         Test t = new Test();
         int k = t.a();
         System.out.println("k = "+(1 * k));    
    }
}

我知道32位的范围是-2,147,483,648到2,147,483,647,所以在此基础上,我期待输出,2,147,483,647但我得到:

k = -2147483648

我甚至试过了

 System.out.println("k = "+(1 * k/2)); 

但仍然输出是:

k = -1073741824

题 :

为什么解决方案是负面的,应该是积极的？

Answer 1

你正在递增你a int的1直到达到1 + Integer.MAX_VALUE,它将其值转换为-2147483648 == Integer.MIN_VALUE.

这是你的循环评论:

// "infinite" loop as a is assigned value 10
while(a > 9)
    // when a reaches Integer.MAX_VALUE, it is still incremented by 1
    ++a;
// loop condition now false, as value for a has shifted to -2147483648
return a;