double或float数据类型不能在循环中正确累加吗？

Question

在循环中，我添加0.10，直到达到所需的＃，然后获取索引。这是我的代码：

    private static int getIndexOfUnits(float units) {
    int index = -1;
    float addup = 0.10f;
    for(float i = 1.00f; i < units; i=(float)i+addup) {
        index++;
        System.out.println("I = " + i + " Index = " + index);
    }

    return index;
}

如果通过的单位是5.7，则我看到的输出是：

I = 1.0 Index = 0
I = 1.1 Index = 1
I = 1.2 Index = 2
I = 1.3000001 Index = 3
I = 1.4000001 Index = 4
I = 1.5000001 Index = 5
I = 1.6000001 Index = 6
I = 1.7000002 Index = 7
I = 1.8000002 Index = 8
I = 1.9000002 Index = 9
I = 2.0000002 Index = 10
I = 2.1000001 Index = 11
I = 2.2 Index = 12
I = 2.3 Index = 13
I = 2.3999999 Index = 14
I = 2.4999998 Index = 15
I = 2.5999997 Index = 16
I = 2.6999996 Index = 17
I = 2.7999995 Index = 18
I = 2.8999994 Index = 19
I = 2.9999993 Index = 20
I = 3.0999992 Index = 21
I = 3.199999 Index = 22
I = 3.299999 Index = 23
I = 3.399999 Index = 24
I = 3.4999988 Index = 25
I = 3.5999987 Index = 26
I = 3.6999986 Index = 27
I = 3.7999985 Index = 28
I = 3.8999984 Index = 29
I = 3.9999983 Index = 30
I = 4.0999985 Index = 31
I = 4.1999984 Index = 32
I = 4.2999983 Index = 33
I = 4.399998 Index = 34
I = 4.499998 Index = 35
I = 4.599998 Index = 36
I = 4.699998 Index = 37
I = 4.799998 Index = 38
I = 4.8999977 Index = 39
I = 4.9999976 Index = 40
I = 5.0999975 Index = 41
I = 5.1999974 Index = 42
I = 5.2999973 Index = 43
I = 5.399997 Index = 44
I = 5.499997 Index = 45
I = 5.599997 Index = 46
I = 5.699997 Index = 47

如果单位是18.90或29.90之类的大数字，则会给出错误的索引。索引通常比应该少1。最初仅添加了0.10，但在添加2.3之后，在添加0.10时得到2.39999....。我相信这是一个精确的问题。如何处理它，并确保无论使用float还是double，我都在大号上获得正确的索引。

有任何想法吗 ！！！！

Answer 1

从浮点指南：

为什么我的数字（例如0.1 + 0.2）加起来不是一轮好0.3，而是得到一个像0.30000000000000004这样的怪异结果？

因为在内部，计算机使用的格式（二进制浮点数）根本无法准确表示一个数字，例如0.1、0.2或0.3。

编译或解释代码时，“ 0.1”已经舍入为该格式的最接近的数字，即使在计算之前，也会产生小的舍入误差。

您不使用，float或者double如果您需要数字来加总。使用BigDecimal代替。