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javacompiler-errors
404 Brain Not Found
404 Brain Not Found

Reputation: 605

'Lossy Conversion' vs. 'Loss of precision'

Can someone please explain/link any documentation that can differentiate between

Possible Loss of Precision Error

and

Lossy Conversion.

I cannot understand which error will occur under what circumstance. Any explanation with examples is deeply appreciated

Upvotes: 0

Views: 431

Answers (2)

Andy Turner
Andy Turner

Reputation: 140309

The difference is the end of the number which gets chopped off:

  • Lossy conversion returns least-significant bits. It is described in JLS Sec 5.1.3:

    A narrowing conversion of a signed integer to an integral type T simply discards all but the n lowest order bits, where n is the number of bits used to represent type T. In addition to a possible loss of information about the magnitude of the numeric value, this may cause the sign of the resulting value to differ from the sign of the input value.

    It is something like converting an int to a byte: you simply get the 8 least-significant bits in this case:

    System.out.println((byte) 258); // 2

  • Loss of precision returns most-significant bits. It is described in JLS Sec 5.1.2:

    A widening primitive conversion from int to float, or from long to float, or from long to double, may result in loss of precision - that is, the result may lose some of the least significant bits of the value.

    It is something like storing an int in a float which is too large to be represented accurately

    int i = (1 << 24) + 1;
float f = i;
System.out.println((int) f == i); // false, because precision is lost.

Upvotes: 1

Hatice
Hatice

Reputation: 944

You get possible loss of precision error when you try to cast such as double to int. You are trying to convert one primitive to another primitive but there is no enough space and you can get loss of your some bytes.

double x = 10.5;             // 8 bytes
int y = x;                   // 4 bytes ;  raises compilation error

You should look for the primitives documentation

Upvotes: 0

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