java 为什么 1 / 2 == 0 使用 double ？
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Why does 1 / 2 == 0 using double?
提问by Benton Justice
I'm a high school student currently getting ready for a state academic meet(UIL). I have a problem and I've looked everywhere and can't seem to find an answer! Why does this print out 0.0?
我是一名高中生，目前正在准备参加州学术会议 (UIL)。我有一个问题，我到处找，似乎找不到答案！为什么这会打印出 0.0？
double d = 1/2;
System.out.println(d);
回答by Suresh Atta
It's because of the data type.
这是因为数据类型。
When you do 1/2that is integer division because two operands are integers, hence it resolves to zero (0.5 rounded down to zero).
当你这样做时1/2是整数除法，因为两个操作数是整数，因此它解析为零（0.5 向下舍入为零）。
If you convert any one of them to double, you'll get a double result.
如果您将其中任何一个转换为双精度，您将得到双精度结果。
double d = 1d/2;
or
或者
double d = 1/2.0;
回答by shmosel
1 and 2 are both integers, so 1 / 2 == 0. The result doesn't get converted to doubleuntil it's assigned to the variable, but by then it's too late. If you want to do float division, do 1.0 / 2.
1 和 2 都是整数，所以1 / 2 == 0。在将结果double分配给变量之前，不会将结果转换为，但为时已晚。如果要进行浮动除法，请执行1.0 / 2.
回答by Bohemian
It's because 1and 2are intvalues, so as per the java language spec, the result of an arithmetic operation on intoperands is also int. Any non-whole number part of the result is discarded - ie the decimal part is truncated, 0.5-> 0
这是因为1和2是int值，所以根据 java 语言规范，对int操作数进行算术运算的结果也是int. 结果的任何非整数部分都被丢弃——即小数部分被截断，0.5->0
There is an automatic widening cast from intto doublewhen the value is assigned to d, but cast is done on the intresult, which is a whole number 0.
当将值分配给 时，会自动从intto扩大强制double转换d，但对int结果进行强制转换，结果是一个整数0。
If "fix" the problem, make one of the operands doubleby adding a "d" to the numeric literal:
如果“修复”问题，请double通过向数字文字添加“d”来创建操作数之一：
double d = 1d/2;
System.out.println(d); // "0.5"
As per the language spec, when one of the operands of an arithmetic operation is double, the result is also double.
根据语言规范，当算术运算的操作数之一是 时double，结果也是double。
回答by Krulig
Cause result of 1/2 = 0 and then result is parsing to double. You're using int instead of double. I think it should be ok:
导致 1/2 = 0 的结果，然后结果解析为双倍。您使用的是 int 而不是 double。我觉得应该没问题：
double d = 1/2.0;
System.out.println(d);
Sorry for weak english
抱歉英语不好
