3.15 The Conditional Operator: ?
3.15 The Conditional Operator: ?The ternary conditional operator allows conditional expressions to be defined. The operator has the following syntax:
If the boolean expression
<condition>
is
true
then
<expression
1
>
is evaluated;
boolean leapYear = false; int daysInFebruary = leapYear ? 29 : 28; // 28
The conditional operator is the expression equivalent of the
if-else
statement. The conditional expression can be nested and the conditional operator
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3.16 Other Operators: new , [] , instanceofThe new operator is used to create objects, that is, instances of classes and arrays. It is used with a constructor call to instantiate classes (see Section 4.4, p. 117), and with the [] notation to create arrays (see Section 4.1, p. 100). It is also used to instantiate anonymous arrays (see Section 4.1, p. 104), and anonymous classes (see Section 7.5, p. 308). Pizza onePizza = new Pizza(); // Create an instance of Pizza class. The [] notation is used to declare and construct arrays and also to access array elements (see Section 4.1, p. 100). int[] anArray = new int[5];// Declare and construct an int array of 5 elements. anArray[4] = anArray[3]; // Element at index 4 gets value of element at index 3.
The boolean, binary, and
Pizza myPizza = new Pizza(); boolean test1 = myPizza instanceof Pizza; // True. boolean test2 = "Pizza" instanceof Pizza; // Compile error. String is not Pizza. boolean test3 = null instanceof Pizza; // Always false. null not an instance.
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Review Questions
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