Safely Casting Long to Int in Java (Updated for Java 8 )

In Java, casting from a long to an int can potentially result in data loss. To address this concern, a safe and idiomatic approach is essential.

Java 8's Math.toIntExact() Method

Prior to Java 8, the recommended method to safely cast a long to an int was to check the result for potential information loss. This involved comparing the cast result with the original long value:

public static int safeLongToInt(long l) {
    int i = (int) l;
    if ((long) i != l) {
        throw new IllegalArgumentException(l   " cannot be cast to int without changing its value.");
    }
    return i;
}

However, in Java 8 and above, a更为简洁有效的方法已被引入：Math.toIntExact()方法。此方法在发生溢出时会抛出ArithmeticException：

import static java.lang.Math.toIntExact;

long foo = 10L;
int bar = toIntExact(foo);

Additional Overflow-Safe Methods in Java 8

In addition to toIntExact(), Java 8 introduced several other overflow-safe methods that end with "exact". These methods perform operations like addition, subtraction, negation, and decrementation while checking for potential overflows:

• Math.incrementExact(long)
• Math.subtractExact(long, long)
• Math.decrementExact(long)
• Math.negateExact(long)
• Math.subtractExact(int, int)

By utilizing Math.toIntExact() and these additional overflow-safe methods, you can safely cast long values to int and perform arithmetic operations without the risk of losing information.