Computer Science
Java Logical Operators
Java Logical Operators are used to combine multiple conditions and return a boolean value. The three logical operators in Java are AND (&&), OR (||), and NOT (!). AND returns true only if both conditions are true, OR returns true if at least one condition is true, and NOT returns the opposite boolean value of the condition.
Written by Perlego with AI-assistance
Related key terms
1 of 5
9 Key excerpts on "Java Logical Operators"
eBook - ePub- Jeanne Boyarsky, Scott Selikoff(Authors)
- 2014(Publication Date)
- Sybex(Publisher)
instanceof operator, while useful for determining whether an arbitrary object is a member of a particular class or interface, is out of scope for the OCA exam.Logical Operators
If you have studied computer science, you may have already come across logical operators before. If not, no need to panic—we'll be covering them in detail in this section.Thelogical operators, (& ), (| ), and (^ ), may be applied to both numeric and boolean data types. When they're applied to boolean data types, they're referred to aslogical operators. Alternatively, when they're applied to numeric data types, they're referred to asbitwise operators, as they perform bitwise comparisons of the bits that compose the number. For the exam, though, you don't need to know anything about numeric bitwise comparisons, so we'll leave that educational aspect to other books.You should familiarize with the truth tables in Figure 2.1 , where x and y are assumed to be boolean data types.Here are some tips to help remember this table:The logical truth tables for & , | , and ^Figure 2.1- AND is only true if both operands are true.
- Inclusive OR is only false if both operands are false.
- Exclusive OR is only true if the operands are different.
Finally, we present the conditional operators, && and || , which are often referred to as short-circuit operators. Theboolean x = true || (y < 4);short-circuit operatorsare nearly identical to the logical operators, & and | , respectively, except that the right-hand side of the expression may never be evaluated if the final result can be determined by the left-hand side of the expression. For example, consider the following statement:Referring to the truth tables, the value x can only be false if both sides of the expression are false. Since we know the left-hand side is true, there's no need to evaluate the right-hand side, since no value of y will ever make the value of x anything other than true. It may help you to illustrate this concept by executing the previous line of code for various values of y
eBook - PDFJava Programming Fundamentals
Problem Solving Through Object Oriented Analysis and Design
- Premchand S. Nair(Author)
- 2008(Publication Date)
- CRC Press(Publisher)
Thus, in a logical expression of the form (logicalExpressionOne || logicalExpressionTwo) if logicalExpressionOne evaluates to true , there is no need to evaluate logicalExpressionTwo . Similarly, in the case of logical operation and false && false = false 138 ■ Java Programming Fundamentals and false && true = false Thus, if the first operand evaluates to false , the value of the second operand has no bear-ing on the final result. Thus, in a logical expression of the form (logicalExpressionOne && logicalExpressionTwo) if logicalExpressionOne evaluates to false , there is no need to evaluate logicalExpressionTwo . Java compiler makes use of these facts and skips the evaluation of operands accordingly. This method of evaluating a logical expression is called the short-circuit evaluation . Advanced Topic 4.5: Additional Logical Operators Java provides two other operators & and | . You can use these operators instead of && and || , respectively, to avoid short-circuit evaluation. Some programmers use them to achieve certain side effects as shown in the following example. Author does not recommend their approach. The following example is given only to illustrate operators & and | . Example 4.10 Consider the following declarations: int numOne = 7, numTwo = 9, numThree = 20; In the case of the following expression, (numOne <= numTwo || numTwo == numThree++) the first operand of the or operator numOne <= numTwo evaluates to true . Due to short-circuit evaluation, second operand (numTwo == numThree++) is never evaluated. Therefore, the variable numThree is not incremented by 1. Thus, numThree is 20 . However, in the following expression, (numOne <= numTwo | numTwo == numThree++) no short-circuit evaluation is performed and the second operand (numTwo == numThree++) is evaluated. The variable numThree is incremented by 1. Thus, numThree becomes 21 .
eBook - PDF- Joyce Farrell(Author)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
138 C H A P T E R 4 Making Decisions Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Using the AND Operator Most programming languages allow you to ask two or more questions in a single comparison by using a conditional AND operator, or more simply, an AND operator that joins decisions in a single expression. For example, if you want to bill an extra amount to cell phone customers who make more than 100 calls that total more than 500 minutes in a billing period, you can use nested decisions, as shown in the previous section, or you can include both decisions in a single expression by writing an expression such as the following: callsMade > CALLS AND callMinutes > MINUTES When you use one or more AND operators to combine two or more Boolean expressions, each Boolean expression must be true for the entire expression to be evaluated as true. For example, if you ask, “Are you a native-born U.S. citizen and are you at least 35 years old?” the answer to both parts of the question must be yes before the response can be a single, summarizing yes. If either part of the expression is false, then the entire expression is false. The conditional AND operator in Java, C11, and C# consists of two ampersands, with no spaces between them (&&). In Visual Basic, you use the keyword And. This book uses AND. One tool that can help you understand the AND operator is a truth table. Truth tables are diagrams used in mathematics and logic to help describe the truth of an entire expression based on the truth of its parts. Quick Reference 4-3 contains a truth table that lists all the possibilities with an AND operator. As the table shows, for any two expressions x and y, the expression x AND y is true only if both x and y are individually true. If either x or y alone is false, or if both are false, then the expression x AND y is false.
eBook - PDF- Joyce Farrell(Author)
- 2012(Publication Date)
- Cengage Learning EMEA(Publisher)
All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. The expressions hoursWorked > HOURS_IN_WK? and dentalPlan = Y? in Figures 3-3 and 3-4 are Boolean expressions. A Boolean expression is one that represents only one of two states, true or false. Every decision you make in a computer program involves evaluating a Boolean expression. True/false evaluation is “ natural ” from a computer ’ s standpoint, because computer circuitry consists of two-state on-off switches, often represented by 1 or 0. Every computer decision yields a true-or-false, yes-or-no, 1-or-0 result. Mathematician George Boole (1815 – 1864) approached logic more simply than his predecessors did, by expressing logical selections with common algebraic symbols. Boolean (true/false) expressions are named for him. Using the Relational Comparison Operators Table 3-1 describes the six relational comparison operators supported by all modern programming languages. These operators are used to create Boolean expressions. Each of these operators is binary — that is, each requires two operands. An operand is a value on either side of an operator. Usually, both operands in a comparison must be the same data type; that is, you can compare numeric values to other numeric values, and text strings to other strings. Operator Name Discussion = Equivalency operator Evaluates as true when its operands are equivalent. Many languages use a double equal sign ( == ) to avoid confusion with the assignment operator. > Greater than operator Evaluates as true when the left operand is greater than the right operand.
eBook - ePubBeginning Java Programming
The Object-Oriented Approach
- Bart Baesens, Aimee Backiel, Seppe vanden Broucke(Authors)
- 2015(Publication Date)
- Wrox(Publisher)
x false?Note that the ! indicates negation. While these operators are used for most primitive data types, there is an exception; Boolean operands can only be compared with equality operators and not with relational operators. That is, true cannot be greater than or less than false ; however, true can be equal to true . Other primitive data types can be compared with both equality and relational operators.It is important to distinguish a single equal sign (= ) from a double equal sign (== ). The first is used for variable assignment. The variable on the left is assigned the value on the right. For example,balance = 5000; assigns the value of 5000 to the variablebalance . The second is a comparison operator to test whether two things are equal. For example,balance == 5000;will return true if the value of the variablebalanceis 5000 and false otherwise.Logical operators, on the other hand, are specific to Booleans, and are used to combine or negate one or more conditions. There are three logical operators: AND (&& ), OR (|| ), and NOT (! ). If two or more Boolean operands are joined using the AND operator, all must evaluate to true for the overall expression to evaluate to true . If they are joined using the OR operator, at least one of them must evaluate to true in order for the overall expression to evaluate to true . Finally, if the NOT operator precedes a Boolean operand that evaluates to true , the overall expression will evaluate to false and vice versa. It evaluates as the opposite of the original expression.Truth tables are used in logic to show the outcome of Boolean operators on pairs of statements. In the first two columns are two statements that can be true or false . In the columns that follow, operators are listed with their results based on whether the statements are true or false . Table 5.2
eBook - PDF- Joyce Farrell(Author)
- 2017(Publication Date)
- Cengage Learning EMEA(Publisher)
138 C H A P T E R 4 Making Decisions Copyright 2018 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. WCN 02-300 Using the AND Operator Most programming languages allow you to ask two or more questions in a single comparison by using a conditional AND operator , or more simply, an AND operator that joins decisions in a single expression. For example, if you want to bill an extra amount to cell phone customers who make more than 100 calls that total more than 500 minutes in a billing period, you can use nested decisions, as shown in the previous section, or you can include both decisions in a single expression by writing an expression such as the following: callsMade > CALLS AND callMinutes > MINUTES When you use one or more AND operators to combine two or more Boolean expressions, each Boolean expression must be true for the entire expression to be evaluated as true. For example, if you ask, “Are you a native-born U.S. citizen and are you at least 35 years old?” the answer to both parts of the question must be yes before the response can be a single, summarizing yes . If either part of the expression is false, then the entire expression is false. The conditional AND operator in Java, C 11 , and C# consists of two ampersands, with no spaces between them (&&). In Visual Basic, you use the keyword And . This book uses AND . One tool that can help you understand the AND operator is a truth table. Truth tables are diagrams used in mathematics and logic to help describe the truth of an entire expression based on the truth of its parts. Quick Reference 4-3 contains a truth table that lists all the possibilities with an AND operator. As the table shows, for any two expressions x and y, the expression x AND y is true only if both x and y are individually true. If either x or y alone is false, or if both are false, then the expression x AND y is false.
eBook - PDF- Kyla McMullen, Elizabeth Matthews, June Jamrich Parsons, , Kyla McMullen, Kyla McMullen, Elizabeth Matthews, June Jamrich Parsons(Authors)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. PROGRAMMING WITH C++ 100 6.4 CONDITIONAL LOGICAL OPERATORS The AND Operator (6.4.1, 6.4.2) A simple conditional statement such as choice == 1 contains a Boolean expression with one relational opera- tor. You can specify more complex logic by adding conditional logical operators for AND and OR conditions. A conditional logical operator combines the outcomes of two or more Boolean expressions. Suppose that you have a menu such as the following: Press or say 1 to connect to an account agent. Press or say 2 to troubleshoot your cable service. Press or say 3 to troubleshoot your Internet service. Press or say 9 to get help. Press or say 0 to quit. Valid input is 0, 1, 2, 3, and 9. You can filter out invalid input such as 4, 5, 6, 7, and 8 with the following: input choice if choice > 3 AND choice != 9 then output "Invalid input." In the conditional expression, when choice is greater than 3 and choice is not 9, then the input is not valid. To determine if the program takes the True or the False path out of the if statement, each of the relational expressions is evaluated and then the results are combined. Suppose the variable choice contains 7. Here’s what the program does: 1. Evaluates choice > 3, which is True because 7 > 3. 2. Evaluates choice != 9, which is True because 7 != 9. 3. Evaluates True AND True from steps 1 and 2, which is True. 4. The result is True and the output is "Invalid input". Q What happens if choice contains 9? A The if statement evaluates to True AND False, which is False.
eBook - ePub- Jeanne Boyarsky, Scott Selikoff(Authors)
- 2019(Publication Date)
- Sybex(Publisher)
- ) operators since you were a little kid. Java supports many other operators that you need to know for the exam. While many should be review for you, some (such as the compound assignment operators) may be new to you.Types of Operators
In general, three flavors of operators are available in Java: unary, binary, and ternary. These types of operators can be applied to one, two, or three operands, respectively. For the exam, you’ll need to know a specific subset of Java operators, how to apply them, and the order in which they should be applied.Java operators are not necessarily evaluated from left-to-right order. For example, the second expression of the following Java code is actually evaluated from right to left given the specific operators involved:int cookies = 4; double reward = 3 + 2 * --cookies; System.out.print("Zoo animal receives: "+reward+" reward points");In this example, you would first decrement cookies to 3 , then multiply the resulting value by 2 , and finally add 3 . The value would then be automatically promoted from 9 to 9.0 and assigned to reward . The final values of cookies and reward would be 9.0 and 3 , respectively, with the following printed:Zoo animal receives: 9.0 reward pointsIf you didn’t follow that evaluation, don’t worry. By the end of this chapter, solving problems like this should be second nature.Operator Precedence
When reading a book or a newspaper, some written languages are evaluated from left to right, while some are evaluated from right to left. In mathematics, certain operators can override other operators and be evaluated first. Determining which operators are evaluated in what order is referred to asoperator precedence. In this manner, Java more closely follows the rules for mathematics. Consider the following expression:var perimeter = 2 * height + 2 * length;The multiplication operator (* ) has a higher precedence than the addition operator (+ ), so the height and length are both multiplied by 2 before being added together. The assignment operator (= ) has the lowest order of precedence, so the assignment to the perimeter
eBook - PDF- Todd Greanier(Author)
- 2006(Publication Date)
- Sybex(Publisher)
The sec-ond operation returns true because the preincrement operator makes the value of a equal to 11. The Conditional Operators You use the conditional operators to test for logical truth. Conditional operators work by testing for truth in two operands. These operands are commonly the result of relational operations that are used to form more complex algorithms. There are six conditional operators: five are binary in nature, and one ( ! ) is unary. ◆ && ◆ || ◆ & ◆ | ◆ ^ ◆ ! The && Operator This operator tests the results of two operands and ensures that both are true . This is sometimes called the Boolean AND operator and is often referred to as a “short-circuit” operator, because it automatically returns false if the first test 84 Chapter 3 returns false . In other words, if the first test fails, this operator does not even test the second operand. Take a look at this operator being used in the following code: int x = 9; int y = 55; boolean b = x < 10 && y > 20; // true boolean c = x == 9 && y == 100; // false boolean d = x == 10 && y == 55; // false In the final line, the y == 55 operation is never executed because the x == 10 operation returned false . The || Operator This operator works a lot like the && operator, except that instead of performing a Boolean AND test, it performs a Boolean OR test. If either of the operations returns true , the || operator returns true . This is also a short-circuit operator because if the first test passes, the second test is not even executed. Take a look at this operator being used in the following code: int x = 9; int y = 55; boolean b = x < 10 || y > 20; // true boolean c = x == 9 || y == 100; // true boolean d = x == 10 || y == 55; // true Notice that all three tests pass in this case even though both relational operations return true only in the first case. The & Operator The & operator is different from the && operator because it has no short-circuit functionality.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
