在java中将两个整数除以一个double

问题描述

我可以看到这是新程序员的常见问题，但是我没有成功地为我的代码实现任何解决方案.基本上我想将 w 和 v 相除，它们必须保存到一个双变量中.但它打印 [0.0, 0.0, ... , 0.0]

I can see this is a common problem for new programmers, however I didn't succeed in implementing any of the solution to my code. Basically I want to divide w and v, which must be saved to a double variable. But it prints [0.0, 0.0, ... , 0.0]

public static double density(int[] w, int[] v){
double d = 0;
    for(L = 0; L < w.length; L++){
        d = w[L]  /v[L];
    }
    return d;
}

推荐答案

这里的这一行 d = w[L]/v[L]; 发生在几个步骤中

This line here d = w[L] /v[L]; takes place over several steps

d = (int)w[L]  / (int)v[L]
d=(int)(w[L]/v[L])            //the integer result is calculated
d=(double)(int)(w[L]/v[L])    //the integer result is cast to double

换句话说，在你转换成双精度之前，精度已经消失了，你需要先转换成双精度，所以

In other words the precision is already gone before you cast to double, you need to cast to double first, so

d = ((double)w[L])  / (int)v[L];

这会强制 java 在整个过程中使用双精度数学，而不是使用整数数学，然后在最后强制转换为双精度

This forces java to use double maths the whole way through rather than use integer maths and then cast to double at the end

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