Narrowing Primitive Cast

ID

java.narrowing_primitive_cast

Severity

low

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

CWE:681, reliability

Description

Reports casts between primitive types that reduce precision or range (narrowing conversions).

Rationale

A narrowing cast silently truncates the value when the source exceeds the target type’s range. For example, (int) 3.9 yields 3 (fractional part lost) and (byte) 300 yields 44 (overflow). These silent truncations are a common source of subtle bugs.

// Bad - double to int loses fractional part
double price = 19.99;
int rounded = (int) price; // 19, not 20

// Bad - long to byte overflows
long big = 100000L;
byte small = (byte) big; // -96, silently overflows

Remediation

Either validate the value before casting or use a method that handles the conversion safely:

// Good - explicit range check
public static int safeLongToInt(long value) {
    if (value < Integer.MIN_VALUE || value > Integer.MAX_VALUE) {
        throw new ArithmeticException("Value out of int range: " + value);
    }
    return (int) value;
}

// Good - use Math.round for floating point
int rounded = (int) Math.round(price);

References