How can I convert a long to int in Java?

Updated, in Java 8:
Math.toIntExact(value);

Original Answer:
Simple type casting should do it:
long l = 100000;
int i = (int) l;

Note, however, that large numbers (usually larger than 2147483647 and smaller than -2147483648) will lose some of the bits and would be represented incorrectly.
For instance, 2147483648 would be represented as -2147483648.

Long x = 100L;
int y = x.intValue();