Oracle Certified Professional: Java SE 17 Developer (1Z0-829) Practice Tests

Explanation

RuntimeException directly extends Exception, which is why all RuntimeException subclasses are unchecked exceptions that do not need to be declared in a throws clause or explicitly caught. Throwable is the superclass of Exception itself, two levels above RuntimeException, not its direct parent. Error is a sibling of Exception under Throwable and is unrelated to the RuntimeException branch. Object is the root of the entire class hierarchy, far above Throwable.

Explanation

Math.round() applies the half-up rounding rule, which rounds toward positive infinity when the fractional part is exactly 0.5. For Math.round(-1.5f), the two nearest integers are -2 and -1. Because the rule favors the direction of positive infinity, -1 is returned rather than -2. For Math.round(-2.5f), the nearest integers are -3 and -2, and rounding toward positive infinity yields -2. Math.round(float) returns an int, and Math.round(double) returns a long. This behavior differs from the intuitive round-half-away-from-zero convention that many developers expect, which would produce -2 and -3 respectively.

Explanation

Math.round() applies the round-half-up rule, which rounds the midpoint case toward positive infinity rather than away from zero. For -1.5f, the two nearest integers are -2 and -1. Since -1 is in the positive direction from -1.5, the method returns -1. This surprises many developers who expect symmetric rounding where -1.5 would round to -2 to mirror the behavior of 1.5 rounding to 2. The Math.round rule is consistent: for any x.5 value, the result is always the higher (more positive) integer. The return type of Math.round(float) is int, while the overload Math.round(double) returns a long. Developers requiring symmetric or decimal-precise rounding should use BigDecimal with an explicit RoundingMode.

Explanation

Math.round is specified as Math.floor(x + 0.5), which rounds toward positive infinity for half-values rather than away from zero. For Math.round(-0.5f): Math.floor(-0.5 + 0.5) = Math.floor(0.0) = 0, returned as int. For Math.round(-1.5): Math.floor(-1.5 + 0.5) = Math.floor(-1.0) = -1, returned as long. The output is 0 followed by -1. Applying symmetric half-away-from-zero logic would incorrectly produce -1 and -2 respectively, but Java's Math.round consistently biases toward positive infinity for exact half-values. The return types also differ: Math.round(float) returns int, while Math.round(double) returns long.

Explanation

Arrays.binarySearch returns a non-negative index when the target is found in the sorted array. When the target is absent, it returns a negative value computed as the bitwise complement of the insertion point, which is equivalent to -(insertion point) - 1. The insertion point is the index at which the target would need to be inserted to maintain sorted order. In the array {3, 7, 11, 15, 22}, the value 9 falls between 7 at index 1 and 11 at index 2. Inserting 9 to preserve ascending order would place it at index 2, so the insertion point is 2. Applying the formula gives -(2) - 1 which equals -3. This encoding ensures that not-found return values never collide with valid found indices, since a successful find always returns a value zero or greater. The array must be fully sorted in ascending order before calling binarySearch; passing an unsorted array produces undefined, unpredictable results.