What does ? in java mean?

The "?" in Java represents the ternary operator, which is used to return different values ​​​​based on a Boolean expression: a true value or a false value is returned based on whether the Boolean expression is true. It is a shorthand form of if-else statement and is used to concisely perform conditional judgments.

The meaning of ? in Java

The ? in Java is a function called the ternary operator (or conditional operator) special operator. It allows returning different values ​​based on a given Boolean expression. Its syntax is as follows:

<布尔表达式> ? <真值> : <假值>

Usage

The first operand of the ternary operator is a Boolean expression that evaluates to true or false. If the Boolean expression is true, the operator returns the second operand (a true value); otherwise, it returns the third operand (a false value).

Example

The following example demonstrates how to use the ternary operator:

int age = 25;
String message = age >= 18 ? "成年人" : "未成年人";

In this example, if age Greater than or equal to 18, message will be set to "Adult"; otherwise, it will be set to "Minor".

Alternative Usage

The ternary operator is the shorthand form of the if-else statement. The above example can be rewritten using the if-else statement as:

int age = 25;
String message;
if (age >= 18) {
    message = "成年人";
} else {
    message = "未成年人";
}

However, the ternary operator is often more concise, especially for the single-row case.

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