{"id":1124,"date":"2020-12-04T14:38:51","date_gmt":"2020-12-04T14:38:51","guid":{"rendered":"https:\/\/blog.samarthya.me\/wps\/?p=1124"},"modified":"2020-12-04T14:40:27","modified_gmt":"2020-12-04T14:40:27","slug":"consumer","status":"publish","type":"post","link":"https:\/\/blog.samarthya.me\/wps\/2020\/12\/04\/consumer\/","title":{"rendered":"Consumer "},"content":{"rendered":"\n

The utility package java.util.function<\/code> has this functional interface Consumer<\/a>. <\/p>\n\n\n\n

Each functional interface (Annotated with @FunctionalInterface<\/a>) conceptually has a single method (abstract) called the functional method to which the lambda expression’s parameter and return types are matched against. Functional interfaces often represent abstract concepts like functions, actions, or predicates.<\/p>\n\n\n\n

Instances of functional interfaces can be created with lambda expressions, method references, or constructor references.<\/p><\/blockquote>\n\n\n\n

Functional interface provide target types for lambda expressions and method references.<\/p>Oracle 8 [Java Doc]<\/cite><\/blockquote><\/figure>\n\n\n\n

Instance methods<\/p>\n\n\n\n

Modifier and Type<\/th>Method and Description<\/th><\/tr>
void<\/code><\/td>accept<\/a>(T<\/a> t)<\/code> Performs this operation on the given argument.<\/td><\/tr>
default Consumer<\/a><T<\/a>><\/code><\/td>andThen<\/a>(Consumer<\/a><? super T<\/a>> after)<\/code> Returns a composed Consumer<\/code> that performs, in sequence, this operation followed by the after<\/code> operation.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Functional interfaces can provide a target type in multiple contexts – assignment context, method invocation, or cast context<\/p>Oracle 8 [Java Doc]<\/cite><\/blockquote><\/figure>\n\n\n\n

Examples<\/h2>\n\n\n\n

Let’s use this Consumer.accept<\/code> method.<\/p>\n\n\n\n

Performs this operation on the given argument. <\/p>

accept(T t)<\/code><\/p><\/blockquote>\n\n\n\n

package me.samarthya;\n\nimport java.util.function.Consumer;\n\npublic class Main {\n\n    public static void ExampleOne() {\n        Consumer<String> myString = (x) -> System.out.println(x);\n        myString.accept(\"Hello World!\");\n    }\n    public static void main(String[] args) {\n        ExampleOne();\n    }\n}<\/code><\/pre>\n\n\n\n
public class Main {\n\n    public static void ExampleOne() {\n        Consumer<String> myString = (x) -> System.out.println(x);\n        myString.accept(\"Hello World!\");\n    }\n    public static void ExampleTwo() {\n        Consumer<List<String>> myList = (x) -> x.stream().sorted().forEach( e -> System.out.println(\" Element: \"+ e));\n        List<String> dummyContents = new LinkedList<String>(){\n            {\n                add(\" Hello\");\n                add(\" World\");\n                add(\"!\");\n            }\n        };\n\n        myList.accept(dummyContents);\n    }\n\n    public static void main(String[] args) {\n        System.out.println(\" Ex1.\");\n        ExampleOne();\n        System.out.println(\" Ex2.\");\n        ExampleTwo();\n    }\n}<\/code><\/pre>\n\n\n\n
andThen(Consumer)<\/h3>\n\n\n\n
public static void ExampleThree() {\n        Consumer<List<String>> toUpper = (x) -> x.replaceAll(String::toUpperCase);\n        Consumer<List<String>> toJoin = (x) -> x.stream().map(e -> String.format(\"%s(%d) \", e, e.length())).forEach(e -> System.out.printf(e));\n\n        List<String> dummyContents = new LinkedList<String>() {\n            {\n                add(\"Hello\");\n                add(\"World\");\n                add(\"!\");\n            }\n        };\n\n        toUpper.andThen(toJoin).accept(dummyContents);\n\n    }\n\n    public static void main(String[] args) {\n        System.out.println(\" Ex3.\");\n        ExampleThree();\n    }<\/code><\/pre>\n\n\n\n
Outputs<\/p>\n\n\n\n
Ex3.\nHELLO(5) WORLD(5) !(1) <\/code><\/pre>\n\n\n\n
Helpers<\/h2>\n\n\n\n