Java 8 Supplier example

In this post, we are going to see about java 8 Supplier interface.
Supplier is functional interface which does not take any argument and produces result of type T.It has a functional method called T get() As Supplier is functional interface, so it can be used as assignment target for lambda expressions.

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Here is source code of Java 8 supplier interface.

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="/sitelet?url=https%3A%2F%2Fjava2blog.com%2Fjava-8-supplier-example%2Fpackage-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();
}

Java 8 Supplier example

Lets use supplier interface to print String:

package org.arpit.java2blog;
import java.util.function.Supplier;

public class Java8SupplierExample {

 public static void main(String[] args) {

  Supplier<String> supplier= ()-> "Arpit";
  System.out.println(supplier.get());
 }
}

It is simple use of supplier interface to get String object. When you run above program, you will get below output:

Let’s create another example using custom class Student.We will use supplier to supply new Student object.

package org.arpit.java2blog;

public class Student {

    private int id;
    private String name;
    private String gender;
    private int age;

    public Student(int id, String name, String gender, int age) {
        super();
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student [id=" + id + ", name=" + name + ", gender=" + gender + ", age=" + age + "]";
    }
}

Now lets create Supplier object which will be used to supply new Student object.

package org.arpit.code2master;

import java.util.function.Supplier;

public class Java8SupplierExample {

    public static void main(String[] args) {

        Supplier studentSupplier = () -> new Student(1, "Arpit", "M", 19);
        Student student = studentSupplier.get();
        System.out.println(student);
    }
}

When you run above program, you will get below output:

public static<T> Stream<T> generate(Supplier<T> s)

package org.arpit.java2blog;

import java.util.Random;
import java.util.function.Supplier;
import java.util.stream.Stream;

public class Java8SupplierExample {

    public static void main(String[] args) {

        Supplier<Integer> randomNumbersSupp=() -> new Random().nextInt(10);
        Stream.generate(randomNumbersSupp)
                        .limit(5)
                        .forEach(System.out::println);
    }

}