In Java, you can convert an int type variable to a long type variable using a type casting operation. Here's an example:

int num = 100;
long l = (long) num;

System.out.println("Long value: " + l); // output: 100

In the above example, we define an int variable num with a value of 100. We then use type casting to convert num to a long variable l. The (long) expression is used to tell the Java compiler to treat the int value as a long.

After the conversion, the value of l is 100, which we verify by printing it to the console using the System.out.println method.

Note that when converting an int to a long, the resulting value can be a larger integer than the original int value. If the int value is negative, the resulting long value will also be negative.