Type parameters can also be declared within method and constructor signatures to create generic methods<\/I> and generic constructors<\/I>. This is similar to declaring a generic type, but the type parameter’s scope is limited to the method or constructor in which it’s declared.
\n\/**
\n * This version introduces a generic method.
\n *\/
\npublic class Box<T> {<\/p>\nprivate T t; <\/p>\n
public void add(T t) {
\n this.t = t;
\n }<\/p>\npublic T get() {
\n return t;
\n }<\/p>\npublic <U> void inspect(U u<\/B>){
\n System.out.println(“T: ” + t.getClass().getName());
\n System.out.println(“U: ” + u.getClass().getName());
\n }<\/B><\/p>\npublic static void main(String[] args) {
\n Box<Integer> integerBox = new Box<Integer>();
\n integerBox.add(new Integer(10));
\n integerBox.inspect(“some text”);
\n }
\n}
\n<\/PRE><\/BLOCKQUOTE>Here we’ve added one generic method, namedinspect<\/CODE>, that defines one type parameter, namedU<\/CODE>. This method accepts an object and prints its type to standard output. For comparison, it also prints out the type ofT<\/CODE>. For convenience, this class now also has amain<\/CODE> method so that it can be run as an application.
\nThe output from this program is: <\/P>
\nT: java.lang.Integer
\nU: java.lang.String
\n<\/PRE><\/BLOCKQUOTE>
\nBy passing in different types, the output will change accordingly. <\/P>
\nA more realistic use of generic methods might be something like the following, which defines a static method that stuffs references to a single item into multiple boxes: <\/P>
public static <U> void fillBoxes(U u, List<Box<U>> boxes) {
\n for (Box<U> box : boxes) {
\n box.add(u);
\n }
\n }<\/p>\n<\/PRE>To use this method, your code would look something like the following:
Crayon red = …;
\n List<Box<Crayon>> crayonBoxes = …;
\n<\/PRE>The complete syntax for invoking this method is:
\nBox.<Crayon>fillBoxes(red, crayonBoxes);
\n<\/PRE><\/BLOCKQUOTE>Here we’ve explicitly provided the type to be used asU<\/CODE>, but more often than not, this can be left out and the compiler will infer the type that’s needed:
\nBox.fillBoxes(red, crayonBoxes); \/\/ compiler infers that U is Crayon
\n<\/PRE><\/BLOCKQUOTE>This feature, known as type inference<\/I>, allows you to invoke a generic method as you would an ordinary method, without specifying a type between angle brackets. <\/BLOCKQUOTE><\/DIV><\/p>\n","protected":false},"excerpt":{"rendered":"Generic Methods and Constructors Type parameters can also be declared within method and constructor signatures to create generic methods and generic constructors. This is similar to declaring a generic type, but the type parameter’s scope is limited to the method or constructor in which it’s declared. \/** * This version introduces a generic method. *\/ … Continue reading Generic Methods and Constructors<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[],"tags":[],"class_list":["post-412","post","type-post","status-publish","format-standard","hentry"],"_links":{"self":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts\/412","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=412"}],"version-history":[{"count":0,"href":"https:\/\/www.strongd.net\/index.php?rest_route=\/wp\/v2\/posts\/412\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=412"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=412"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.strongd.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=412"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}