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Illustration of relational operators
The program shown in Listing 2 illustrates the result of applying relational operators in Java. The output is shown in thecomments at the beginning of the program. Note that the program automatically displays true and false as a result of applying the relational operators.
| Listing 2 . Illustration of relational operators. |
|---|
/*File relat01.java Copyright 1997, R.G.Baldwin
Illustrates relational operators.Output is
The relational 6<5 is false
The relational 6>5 is true
*********************************************************/class relat01 { //define the controlling class
public static void main(String[]args){ //main method
System.out.println("The relational 6<5 is "
+(6<5));
System.out.println("The relational 6>5 is "
+(6>5));
}//end main}//End relat01 class. |
Conditional operators
The relational operators are often combined with another set of operators (referred to as conditional or logical operators) to construct more complex expressions.
Java supports three such operators as shown in the following table.
Operator Typical Use Returns true if&&Left&&Right Left and Right are both true
|| Left || Right Either Left or Right is true! ! Right Right is false The operands shown in the table must be boolean types, or must have been created by the evaluation of an expression that returns a boolean type.
Left to right evaluation
An important characteristic of the behavior of the logical and andthe logical or operators is that the expressions are evaluated from left to right, and the evaluation of the expression is terminated as soon as the resultof evaluating the expression can be determined.
For example, in the following expression, if the variable a is less than the variable b , there is no need to evaluate the right operand of the || to determine that the result of evaluating the entire expression would be true . Therefore, evaluation will terminate as soon as the answer can be determined.
(a<b) || (c<d) Don't confuse bitwise and with logical and
As discussed in the next section, the symbols shown below are the bitwise and and the bitwise or .
&bitwise and
| bitwise or One author states that in Java, the bitwise and operator can be used as a synonym for the logical and and the bitwise or can be used as a synonym for the logical inclusive or if both of the operands are boolean . (I recommend that you don't do that because it could cause confusion for someonereading your code.)
Note however that according to a different author, in this case, the evaluation of the expression is not terminated until all operands have beenevaluated, thus eliminating the possible advantage of the left-to-right evaluation.
Java provides a set of operators that perform actions on their operands one bit at a time as shown in the following table.
Operator Typical Use Operation>>OpLeft>>Dist Shift bits of OpLeft right
by Dist bits (signed)<<OpLeft<<Dist Shift bits of OpLeft left
by Dist bits>>>OpLeft>>>Dist Shift bits of OpLeft right
by Dist bits (unsigned)&OpLeft&OpRight Bitwise and of the
two operands| OpLeft | OpRight Bitwise 
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