Given the code fragment: String str = "Java is a programming language"; ToIntFunction<String> indexVal = str :: indexOf; //line n1 int x = indexVal.applyAsInt("Java"); //line n2…

Question

Options

• A0
• B1
• CA compilation error occurs at line n1.
• DA compilation error occurs at line n2.

• A
  85% (22)
• B
  8% (2)
• C
  4% (1)
• D
  4% (1)

Explanation

Option A is correct because str.indexOf("Java") returns 0 - Java uses zero-based indexing, and the substring "Java" begins at the very first character of "Java is a programming language".

Option B (1) is wrong because Java string indices start at 0, not 1; confusing zero-based with one-based indexing is the classic trap this distractor is baiting.

Option C is wrong because the method reference str::indexOf is perfectly valid - String.indexOf(String) accepts a String and returns an int, which matches ToIntFunction<String>'s abstract method signature int applyAsInt(String t) exactly.

Option D is wrong because applyAsInt("Java") is the correct way to invoke a ToIntFunction<String>, and passing a String literal is valid, so no compilation error occurs.

Memory tip: When you see a method reference bound to a specific instance (object::method), mentally substitute it as a lambda - str::indexOf is equivalent to s -> str.indexOf(s). Ask yourself: does the parameter type and return type match the functional interface? If yes, it compiles. And always remember: indexOf at position zero returns 0, not 1.

No community discussion yet for this question.