What does: in java mean?

Meaning of : in Java

In the Java programming language, the colon (:) is used as a delimiter for type declarations. When you declare a variable or method parameter, a colon separates the variable or parameter's name from its data type.

Declare variables

<code class="java">int age = 25;
String name = "John Doe";</code>

In this case, the "int" and "String" after the colon represent the data types of the "age" and "name" variables respectively. . This provides the Java compiler with information about the type of data the variable is expected to store and helps ensure type safety.

Declare method parameters

<code class="java">public void printName(String name) {
    System.out.println(name);
}</code>

In the method declaration, the "String" after the colon specifies the data type of the "name" parameter. This tells the compiler that the method accepts a parameter of type String.

Type Annotations

Java 8 introduced type annotations, allowing developers to provide more detailed type information for variables and method parameters. A colon is used as part of this syntax.

<code class="java">@NonNull String name;</code>

In this example, "@NonNull" after the colon means that the "name" variable cannot be null. This helps improve code readability and reduces errors.

Type parameterization

The colon is also used to parameterize generic types. Generic types allow the definition of classes or interfaces that can store various data types.

<code class="java">List<String> names = new ArrayList<>();</code>

In this case, the "String" after the colon specifies the type parameter of the "names" list. This means that the list will store data elements of type String.

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