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Pseudo Code to Java translation error

I have a question about an error when translating the pseudo code below into Java. There is no problem with the loss of accuracy because of truncation but a programming language issue that I can't seem to find.

I though the answer would be that the result of Math.pow() would be too much for a double (range from 4.94065645841246544e-324d to 1.79769313486231570e+308d. But apparently there is more wrong and I can't see it.

PSEUDO CODE

x = 7.0
y = x^1000.0
n = y truncated to an integer

converted to

JAVA

double x, y;
int n; 

x = 7.0;
y = Math.pow(x,1000.0);
n = (int)y;

Much appreciated, I'd really like to understand the issues here.

Solution

  • When you do,

    double x = 7.0;
double y = Math.pow(x, 1000.0); // <-- INFINITY

    you do exceed the precision of double and you get Double.POSITIVE_INFINITY

    System.out.println(y);

    Output is

    Infinity

    When you cast that to int you get Integer.MAX_VALUE which is 2^31-1 or 2147483647. If you want to get a more convincing result you could use BigInteger like

    int n = BigInteger.valueOf(7).pow(1000).intValue();
System.out.println(n);

    Output is

    432069569

    Of course, the real result is obtained by

    System.out.println(BigInteger.valueOf(7).pow(1000));

    Which results in a very big number indeed.