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Supplier is a Functional Interface, so it only contains an abstract method as follows:
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package java.util.function; /** * Represents a supplier of results. * * <p>There is no requirement that a new or distinct result be returned each * time the supplier is invoked. * * <p>This is a <a href="package-summary.html">functional interface</a> * whose functional method is {@link #get()}. * * @param <T> the type of results supplied by this supplier * * @since 1.8 */ @FunctionalInterface public interface Supplier<T> { /** * Gets a result. * * @return a result */ T get(); } |
This interface simply returns the value in the context that is being used by the get() method.
For example, we have the following list:
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List<String> s = Arrays.asList("Khanh", "Quan"); |
Now that I want to use the Supplier interface to get the value of each element in the list and print out to the console, I will write a method like this:
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private void print(Supplier supplier) { System.out.println(supplier.get()); } |
And now we can use this method:
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package com.huongdanjava.javaexample; import java.util.Arrays; import java.util.List; import java.util.function.Supplier; public class Example { public static void main(String[] args) { List<String> s = Arrays.asList("Khanh", "Quan"); s.stream().forEach(x -> print(() -> x)); } private static void print(Supplier supplier) { System.out.println(supplier.get()); } } |
In the above code, instead of using the Consumer interface, I used the print() method with the Supplier interface parameter, which is the value of each element in the list.
Result:
Like the Consumer interface, here are some variations of the Supplier interface:
- Interface IntSupplier: The getAsInt() method returns the Integer value.
- Interface DoubleSupplier: with the getAsDouble() method returns a Double value.
- LongSupplier interface: with the getAsLong() method returns a Long value.
- Interface BooleanSupplier: The getAsBoolean() method returns the Integer value.
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