小编Eur*_*oco的帖子

我正在学习Java,而我正在尝试一些小程序.我有这个问题:

/*
 Compute the number of cubic inches
 in 1 cubic mile.
*/
class Inches {
    public static void main(String args[]) {
        int ci;
        int im;

        im = 5280 * 12;

        ci = im * im * im;

        System.out.println("There are " + ci + " cubic inches in cubic mile.");
    }
}

输出是:

There are 1507852288 cubic inches in cubic mile.

我知道整数的位宽是32,所以范围是:-2,147,483,648到2,147,483,647

为什么输出1507852288？它应该是2,147,483,647.

谢谢.

我正在用Herbert Schildt的书来学习Java:Java初学者指南.在那本书中出现了这段代码:

// A promotion surprise!
class PromDemo{
    public static void main(String args[]){
        byte b;
        int i;
        b = 10;
        i = b * b;      // OK, no cast needed

        b = 10;
        b = (byte) (b * b);     // cast needed!!

        System.out.println("i and b: " + i + " " + b);
    }
}

我不明白为什么我必须在行中使用(byte):

b = (byte) (b * b);     // cast needed!!

b被定义为一个字节,b*b的结果是100,这是一个字节的正确值(-128 ... 127).

谢谢.

我正在学习Java"Java:A Beginner's Guide"一书.这本书展示了for循环的这个例子:

// Loop until an S is typed
class ForTest {
    public static void main (String args[]) throws java.io.IOException {

        int i;

        System.out.println ("Press S to stop.");

        for (i=0; (char) System.in.read() != 'S'; i++)
                System.out.println ("Pass #" + i);
    }
}

输出是:

Press S to stop.
s
Pass #0
Pass #1
Pass #2
d
Pass #3
Pass #4
Pass #5
S

我不明白为什么每次按下不同的键盘键时,它会写三次Pass#.我认为它应该只写一次Pass#.谢谢.

我试图理解按位和移位运算符.我写了一个简单的代码来向我展示一个短类型的位.

class Shift {
    public static void main (String args[]) {
        short b = 16384;

        for (int t = 32768; t > 0; t = t / 2) {
            if ((b&t) != 0) System.out.print("1 ");
            else System.out.print ("0 ");
        }
        System.out.println();
        b = (short)(b + 2);
        for (long t = 2147483648L; t > 0; t = t / 2) {
            if ((b&t) != 0) System.out.print ("1 ");
            else System.out.print ("0 ");
        }
        System.out.println();
    }
}

输出是:

C:\>java Shift
0 1 …