Convert Long into Integer

Question

How to convert a Long value into an Integer value in Java?

Answer 1

The best simple way of doing so is:

public static int safeLongToInt( long longNumber ) 
    {
        if ( longNumber < Integer.MIN_VALUE || longNumber > Integer.MAX_VALUE ) 
        {
            throw new IllegalArgumentException( longNumber + " cannot be cast to int without changing its value." );
        }
        return (int) longNumber;
    }

Answer 2

In Java 8 you can use Math.toIntExact. If you want to handle null values, use:

Integer intVal = longVal == null ? null : Math.toIntExact(longVal);

Good thing about this method is that it throws an ArithmeticException if the argument (long) overflows an int.

Answer 3

You'll need to type cast it.

long i = 100L;
int k = (int) i;

Bear in mind that a long has a bigger range than an int so you might lose data.

If you are talking about the boxed types, then read the documentation.

Answer 4

In java ,there is a rigorous way to convert a long to int

not only lnog can convert into int,any type of class extends Number can convert to other Number type in general,here I will show you how to convert a long to int,other type vice versa.

Long l = 1234567L;
int i = org.springframework.util.NumberUtils.convertNumberToTargetClass(l, Integer.class);

Answer 5

If you care to check for overflows and have Guava handy, there is Ints.checkedCast():

int theInt = Ints.checkedCast(theLong);

The implementation is dead simple, and throws IllegalArgumentException on overflow:

public static int checkedCast(long value) {
  int result = (int) value;
  checkArgument(result == value, "Out of range: %s", value);
  return result;
}

Answer 6

In addition to @Thilo's accepted answer, Math.toIntExact works also great in Optional method chaining, despite it accepts only an int as an argument

Long coolLong = null;
Integer coolInt = Optional.ofNullable(coolLong).map(Math::toIntExact).orElse(0); //yields 0