[JAVA][Beginning Java 8 Games Development]

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Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles Java Logical Operators: The Java logical operators are similar to the boolean operations (union, intersection, etc.) that you learned about in school, and allow you to determine if both boolean variables hold the same value (AND), or if one of the boolean variables is different (OR), from the other. There’s also a NOT operator that reverses the value of any of the compared boolean operands. Table 3-4 shows Java’s three logical operators, and an example of each, along with a description. Table 3-4. Java Logical Operators, an Example in Which A = True and B = False, and a Description of Logical Operation Operator Example Description && (A && B) is false A logical AND operator equates to true when BOTH operands are the same value. || (A || B) is true A logical OR operator equates to true when EITHER operand is the same value. ! !(A && B) is true A logical NOT operator reverses the logical state of the operator (or set) it is applied to. Let’s use logical operators to enhance the game logic example in the previous section by including the direction in which the InvinciBagel is moving on the screen. The existing facingDirection String variable will control the direction the InvinciBagel is facing (and moving in, if in motion). You can now use the following logical operator to determine if the InvinciBagel is facing left (W, or West); if the travelingWest boolean variable is true; AND if the hit (or passed) boolean variable on the left-hand side of the screen, hitLeftSideScrn, is also equal to true. The modified code for doing this will include two more boolean variable declarations and initializations and will look like this: boolean changeDirection = false; // Create boolean variable changeDirection, initialize to false boolean hitLeftSideScrn = false; // Create boolean variable hitLeftSideScrn, initialize to false boolean travelingWest = false; // Create boolean variable travelingWest, initialize to false hitLeftSideScrn = (invinciBagelX
Chapter 3 ■ A Java 8 Primer: An Introduction to Java 8 Concepts and Principles Table 3-5. Java Assignment Operators, What Each Assignment Is Equal to in Code, and a Description of the Operator Operator Example Description = C=A+B Basic assignment operator: Assigns value from right-hand operand to left-hand operand += C+=A equals C=C+A ADD assignment operator: Adds right-hand operand to left-hand operand; puts result in left-hand operand -= C-=A equals C=C-A SUB assignment operator: Subtracts right-hand operand from left-hand operand; puts result in left-hand operand *= C*=A equals C=C*A MULT assignment operator: Multiplies right-hand operand and left-hand operand; puts result in left-hand operand /= C/=A equals C=C/A DIV assignment operator: Divides left-hand operand by right-hand operand; puts result in left-hand operand %= C%=A equals C=C%A MOD assignment operator: Divides left-hand operand by right-hand operand; puts remainder in left-hand operand Finally, you are going to take a look at conditional operators, which also allow you to code powerful game logic. Java Conditional Operators The Java language also has a conditional operator that can evaluate a condition and make a variable assignment for you, based on the resolution of that condition, using only one compact programming construct. The generic Java programming statement for a conditional operator always uses the following basic format: Variable = (evaluated expression) ? Set this value if TRUE : Set this value if FALSE ; So, on the left-hand side of the equals sign, you have the variable, which is going to change (be set), based on what is on the right-hand side of the equals sign. This conforms to what you have learned thus far. On the right-hand side of the equals sign, you have an evaluated expression, for instance, “x is equal to 3,” followed by a question mark and then two numeric values that are separated from each other, using the colon, and, finally, a semicolon to terminate the conditional operator statement. If you wanted to set a variable y to a value of 25 if x is equal to 3, and to 10 if x is not equal to 3, you would write that conditional operator programming statement by using the following Java programming logic: y = (x == 3) ? 25 : 10 ; Next, you are going to look at Java logic control structures that leverage the operators you just learned about. Java Conditional Control: Decision Making or Loops As you have just seen, many of the Java operators can have a fairly complex structure and provide a lot of processing power, using very few characters of Java programming logic. Java also has several more complicated conditional control structures, which can automatically make decisions or perform repetitive tasks for you, once you have set up the conditions for those decisions or task repetitions by coding the Java logic control structure. www.it-ebooks.info 65
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Contents at a Glance About the Auth
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Introduction The Java Programming L
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■ Introduction In Chapter 13 you
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Chapter 1 ■ Setting Up a Java 8 G
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Chapter 6 The Foundation of Game De
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Chapter 8 Creating Your Actor Engin
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Chapter 8 ■ Creating Your Actor E
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Chapter 10 Directing the Cast of Ac
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Chapter 12 Setting Boundaries for Y
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Chapter 13 ■ Animating Your Actio
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Chapter 14 ■ Setting Up the Game
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Chapter 15 Implementing Game Audio
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Chapter 15 ■ Implementing Game Au
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Chapter 16 ■ Collision Detection:
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Chapter 17 Enhancing Game Play: Cre
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Chapter 17 ■ Enhancing Game Play:
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■ index Background image (cont.)
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■ index InvinciBagel animation (c
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■ index Modifier keywords access
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Beginning Java 8 Games Development
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This Java 8 Game Development book i
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■ Contents NetBeans 8.0 Is User I
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■ Contents ■■Chapter 5: An In
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■ Contents Creating a Hero Superc
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■ Contents Organizing the .update
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■ Contents Optimizing the Scene G
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About the Author Wallace Jackson ha
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Acknowledgments I would like to ack
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