Java / Design Patterns
Explain telescopic constructor pattern in Java.
In Java there is no support for default values for constructor parameters.
Telescoping constructor comes to the rescue. A class has multiple constructors, where each constructor calls a more specific constructor in the hierarchy, which has more parameters than itself, providing a default value for the extra parameters. The next constructor does the same until there is no left.
public Person(String firstName, String lastName) { this(firstName, lastName, null); } public Person(String firstName, String lastName, String description) { this(firstName, lastName, description, 0); } public Person(String firstName, String lastName, String description, int age) { this.firstName = firstName; this.lastName = lastName; this.description = description; this.age = age; }
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