Binary operations java
It should be noted that, when given a boolean logical operator, the JVM checks as few operands as possiblefrom left to right. For example, if the first operator of an Binary operations java expression is truethen the expression will be true no matter what the second operand is. This is called short-circuit evalution and is important if the second operand is a method call. Consider the following methods:. If the go binary operations java is called, the output is.
The JVM hits the if statement and looks at the first operand — here, the true literal. The expression could still go either way: So the Binary operations java checks the second operand; since it's a method call, the method is called in its entirety. What if the first operand was the false literal?
Remember, an AND expression is only binary operations java if both operands are true. Because the second operand is never checked, the method is never called, and the output is. Usually, short-circuit evaluation is a good thing, because it saves running time. But if the second operand is a method call that changes something binary operations java returning a value, you might want to force the method to run no matter what. To do this, use the long-circuit logical operators.
They're the same as the bitwise operatorsbut they operate logically when applied to booleans. They're exactly the same as the short-circuit boolean operators, only not doubled. Note that there is no short-circuit form of the XOR operator, because, mathematically, it always needs to evaluate both its arguments to compute its result.
If you use a bitwise operator in a boolean expression, both operands are always evaluated. Consider the above code again. If binary operations java go method is rewritten:. Because the showFalse method will be called even though the first operand the false literal alone determines the result of the entire expression. The other use of the bitwise operators is manipulating individual bits in an int.
Note that binary operations java operands can be any integral type; but if it is a type smaller than intit will be promoted to an int type, and the result will be int. The bitwise NOT is a unary operator it takes only one operand that flips every bit in its operand. The result of a bitwise OR has on-bits where either or both of its operands has an on-bit.
The left-shift operator shifts the bits of the first operand left by the number of places specified by the second operand.
Bits shoved off the left side are lost; empty bits on the right are filled in with zeros. The right-shift operator keep bits shifts the bits of the first operand right by the number of places specified by the second operand. Bits shoved off the right side are lost; bits on the left side are the same as the original binary operations java bit the "sign bit". The right-shift operator force bits is the same as the right-shift keep operator. However, the new bits on the left are always set to zero.
Integer variables are frequently intended to represent either a numeric value or a bit collection. Numeric values must be exclusively operated on using arithmetic operations, whereas bit collections must be exclusively operated on using bitwise operations. Performing bitwise and arithmetic operations on binary operations java same data can obscure the purpose of the data stored in the variable and often indicates confusion regarding that purpose.
Unfortunately, bitwise operations are frequently performed on arithmetic values as a form of premature optimization. Although such operations are valid and will compile, they can reduce code readability. Left- and right-shift operators are often employed to multiply or divide a number by a power of two.
This approach compromises code readability and portability for the sake of often-illusory speed gains. The Java Virtual Machine JVM usually makes such optimizations automatically, and, unlike a programmer, the JVM can optimize for the implementation details of the current platform.
This noncompliant code example includes both bitwise and arithmetic manipulations of the integer x that conceptually contains a numeric value. This noncompliant code example segregates arithmetic and bitwise operators by variables. The x variable participates only in bitwise operations, and y participates only in arithmetic operations. This example is noncompliant because the actual data has both bitwise and arithmetic operations performed on it, even though the operations are performed on different variables.
In this compliant solution, the assignment statement is modified to reflect the arithmetic nature of xresulting in a clearer indication of the programmer's intentions. A reviewer could now recognize that the operation should also be checked for overflow. The need for an overflow check might not have been apparent in the original, noncompliant code example see NUMJ.
Detect or prevent integer overflow for more information. In this noncompliant code example, the programmer wishes to divide x by 4. In a misguided attempt to optimize performance, the programmer binary operations java a right-shift operation rather than a division operation. Using logical right shift for division produces an incorrect result when the dividend x in this example contains a negative value.
After this code sequence is run, x contains the value rather than the binary operations java Arithmetic right shift truncates the resulting value toward negative infinity, whereas integer division truncates toward zero. In this binary operations java code example, a programmer attempts to fetch four values from a byte array and pack them into the binary operations java variable result. The integer value in this example represents a bit collection, not a numeric value.
In the bitwise operation, the value of the byte array element b[i] is promoted to an int by sign extension. When a byte array element contains a negative value for example, 0xffthe sign extension propagates 1-bits into the upper binary operations java bits of the int.
This behavior might be unexpected if the programmer is assuming that byte is an unsigned type. In this example, adding the promoted byte values to result fails to result in a packed integer representation of the bytes [ FindBugs ]. This noncompliant code example masks off the upper 24 bits of the promoted byte array element before performing the addition. The number of bits required to mask the sizes of byte and int are specified by The Java Language Specification.
Although this code calculates the correct result, it violates this rule by combining bitwise and arithmetic operations on the binary operations java data. This compliant solution masks off the upper 24 bits of the promoted byte array element. The result is then combined with result using a logical OR operation. Nevertheless, as a matter of style, it is preferable to replace such constant expressions with the equivalent hexadecimal constants. Data that is normally treated arithmetically may be treated with bitwise operations for the purpose of serialization or deserialization.
This alternative treatment is often required for reading or writing the data from binary operations java file or network socket. Bitwise operations are also permitted when reading or writing the data from a tightly packed data structure of bytes.
Performing bitwise manipulation and arithmetic operations on the same variable obscures the programmer's intentions and reduces readability.
Consequently, it is more difficult for a binary operations java auditor or maintainer to determine which checks must be performed to eliminate security flaws and ensure data integrity. For instance, overflow checks are critical for numeric types that undergo arithmetic operations but less critical for numeric types that undergo bitwise operations. Avoid performing bitwise and arithmetic operations on the same data. They contain no conflicting use of the variable x.
Rather, we are just stating that x is intended for arithmetic use. I think we should limit the rule to the case of conflicting uses of the same variable.
If not, then we should make explicit how we judge the "kind" of an integer variable in the absence of any external indications of its kind. Is it permitted to compare two values of different kind? Seems like it should be forbidden, but I don't know the practical implications such a restriction.
I found this snippet in com. ChannelX11line I'm not sure what to make of it -- should it be allowed or not? Binary operations java far binary operations java I can tell, it is ensuring that the second argument is word aligned for a 4 byte word. The method used is very direct, yet it seems that it should be an arithmetic calculation, not the bit trick used here. Still, i'm skeptical that this kind of optimization would be found by a compiler.
The arithmetic version would be. Binary operations java would expect any decent compiler to generate the binary operations java code for either expression. A t tachments 0 Page History. Noncompliant Code Example Left Shift Left- and right-shift binary operations java are often employed to multiply or divide a number by a power of two.
Do not perform bitwise and arithmetic operations on the same data LiveLesson [ Steele ]. Permalink Feb binary operations java, I'd say it is permitted, simply because no one has tried to argue otherwise.
Permalink May 10, Permalink Aug 15, I've fixed it, thanks! Powered by Atlassian Confluence 6. Do not perform bitwise and arithmetic operations on the same data LiveLesson.