Which code fragment cause a compilation error?

Question

Options

• Afloat flt = 100F;
• Bfloat flt = (float) 1_11.00;
• Cfloat flt = 100;
• Ddouble y1 = 203.22; float flt = y1;
• Eint y2 = 100; float flt = (float) y2;

• A
  4% (1)
• B
  12% (3)
• D
  80% (20)
• E
  4% (1)

Explanation

Option D fails to compile because assigning a double variable directly to a float variable is a narrowing conversion - Java will not do this implicitly, since double (64-bit) is wider than float (32-bit) and data could be lost. Adding an explicit cast (float) y1 would fix it.

Why the distractors compile successfully:

• A - The F suffix explicitly declares the literal as a float, so no conversion is needed.
• B - The explicit (float) cast handles the narrowing of the double literal; underscores in numeric literals (1_11) are valid since Java 7.
• C - Assigning an int literal to float is a widening conversion, which Java allows implicitly.
• E - The explicit (float) cast legally narrows the int variable to float.

Memory tip: Think "widening is free, narrowing needs a fee (a cast)" - Java freely promotes smaller types upward (int → float → double), but going down the hierarchy always requires an explicit cast or you'll pay with a compilation error.

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