Operators in Java

Encoding Quick Response Code in Java Operators

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These operators are unique in that they can appear both in postfix form, where they follow the operand as just shown, and prefix form, where they precede the operand In the foregoing examples, there is no difference between the prefix and postfix forms However, when the increment and/or decrement operators are part of a larger expression, then a subtle, yet powerful, difference between these two forms appears In the prefix form, the operand is incremented or decremented before the value is obtained for use in the expression In postfix form, the previous value is obtained for use in the expression, and then the operand is modified For example:

x = 42; y = ++x;

In this case, y is set to 43 as you would expect, because the increment occurs before x is assigned to y Thus, the line y = ++x; is the equivalent of these two statements:

x = x + 1; y = x;

However, when written like this,

x = 42; y = x++;

the value of x is obtained before the increment operator is executed, so the value of y is 42 Of course, in both cases x is set to 43 Here, the line y = x++; is the equivalent of these two statements:

y = x; x = x + 1;

// Demonstrate ++ class IncDec { public static void main(String args[]) { int a = 1; int b = 2; int c; int d; c = ++b; d = a++; c++; Systemoutprintln("a = " + a); Systemoutprintln("b = " + b); Systemoutprintln("c = " + c); Systemoutprintln("d = " + d); } }

Part I:

Java defines several bitwise operators that can be applied to the integer types, long, int, short, char, and byte These operators act upon the individual bits of their operands They are summarized in the following table:

Operator ~ & | ^ >> >>> << &= |= ^= >>= >>>= <<= Result Bitwise unary NOT Bitwise AND Bitwise OR Bitwise exclusive OR Shift right Shift right zero fill Shift left Bitwise AND assignment Bitwise OR assignment Bitwise exclusive OR assignment Shift right assignment Shift right zero fill assignment Shift left assignment

Since the bitwise operators manipulate the bits within an integer, it is important to understand what effects such manipulations may have on a value Specifically, it is useful to know how Java stores integer values and how it represents negative numbers So, before continuing, let s briefly review these two topics All of the integer types are represented by binary numbers of varying bit widths For example, the byte value for 42 in binary is 00101010, where each position represents a power of two, starting with 20 at the rightmost bit The next bit position to the left would be 21, or 2, continuing toward the left with 22, or 4, then 8, 16, 32, and so on So 42 has 1 bits set at positions 1 3 5 1, 3, and 5 (counting from 0 at the right); thus, 42 is the sum of 2 + 2 + 2 , which is 2 + 8 + 32 All of the integer types (except char) are signed integers This means that they can represent negative values as well as positive ones Java uses an encoding known as two s complement, which means that negative numbers are represented by inverting (changing 1 s to 0 s and vice versa) all of the bits in a value, then adding 1 to the result For example, 42 is represented by inverting all of the bits in 42, or 00101010, which yields 11010101, then adding 1, which results in 11010110, or 42 To decode a negative number, first invert all of the bits, then add 1 For example, 42, or 11010110 inverted, yields 00101001, or 41, so when you add 1 you get 42

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