SCJP Java Operators, Type Casting, and Assignments

Question 1

What is the result of the expression `6 & 3` in Java?

Accepted Answer

2

Answer

The & operator performs a bitwise AND. 6 in binary is 110 and 3 is 011. ANDing each bit: 110 & 011 = 010, which equals 2.

Question 2

What is the value of `byte b = (byte) 130;` in Java?

Accepted Answer

-126

Answer

byte holds values from -128 to 127. 130 in binary (8 bits) is 10000010. With a signed byte, the leading 1 indicates a negative number. Using two's complement, this equals -126.

Question 3

What does the compound assignment `x += 1.5;` do when x is declared as `int x = 3;`?

Accepted Answer

Assigns 4 to x after an implicit narrowing cast

Answer

Compound assignment operators include an implicit narrowing cast. `x += 1.5` is equivalent to `x = (int)(x + 1.5)`, so 3 + 1.5 = 4.5 is truncated to 4. A plain `x = x + 1.5` would fail to compile.

Question 4

What is the output of `System.out.println(1 + 2 + "3" + 4 + 5);`?

Accepted Answer

3345

Answer

Evaluation is left-to-right. `1 + 2` = 3 (int addition), then `3 + "3"` = "33" (string concatenation), then "33" + 4 = "334", then "334" + 5 = "3345".

Question 5

What is the result of `System.out.println(5 >> 1);`?

Accepted Answer

2

Answer

The >> operator is the signed right-shift. Shifting 5 (binary 101) right by 1 position gives 010, which is 2. Each right-shift by 1 is equivalent to integer division by 2.

SCJP - Sun Certified Java Programmer Practice Test

SCJP - Sun Certified Java Programmer Practice Test

SCJP Java Operators, Type Casting, and Assignments