Java 8 – Supplier | Code Factory

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Sometimes our requirement is we have to get some value based on some operation like

supply Student object

Supply Random Name

Supply Random OTP

Supply Random Password

etc

• For this type of requirements we should go for Supplier
• Supplier can be used to supply items(objects)
• Supplier won’t take any input and it will always supply objects
• Supplier Functional Interface contains only one method get()

@FunctionalInterface
public interface Supplier<T> {
    T get();
}

Supplier Functional interface does not contain any default and static methods.

Program to generate random name :

package com.codeFactory.supplier;

import java.util.function.Supplier;

public class Test {
	public static void main(String... args) {
		Supplier<String> s = () -> {
			String[] s1 = {"Narendra", "Amit", "Yogi", "Rahul"};
			int x = (int) (Math.random() * 4);
			return s1[x];
		};
		
		System.out.println(s.get());
		System.out.println(s.get());
		System.out.println(s.get());
	}
}

Output :

Narendra
Amit
Rahul

. . . . .

Program to get System Date by using Supplier :

package com.codeFactory.supplier;

import java.util.Date;
import java.util.function.Supplier;

public class Test {
	public static void main(String... args) {
		Supplier<Date> s = () -> new Date();
		System.out.println(s.get());
	}
}

Output :

Wed Apr 29 13:27:58 IST 2020

. . . . .

Program to generate 5 digit random OTP :

package com.codeFactory.supplier;

import java.util.function.Supplier;

public class Test {
	public static void main(String... args) {
		Supplier<String> otp = () -> {
			String s = "";
			for(int i=0; i<5; i++) {
				s = s + (int) (Math.random() * 10);
			}
			return s;
		};
		
		System.out.println(otp.get());
		System.out.println(otp.get());
		System.out.println(otp.get());
	}
}

Output :

33325
89449
53473

. . . . .

Program to generate random password :

Rules :

• length should be 8 characters
• 2, 4, 6, 8 places only digits
• 1, 3, 5, 7 only Capital Uppercase characters, @, #, $

package com.codeFactory.supplier;

import java.util.function.Supplier;

public class Test {
	public static void main(String... args) {
		Supplier<String> s = () -> {
			String symbols = "ABCDEFGHIJKLMNOPQRSTUVWXYZ#$@";
			Supplier<Integer> d = () -> (int)(Math.random() * 10);
			Supplier<Character> c = () -> symbols.charAt((int)(Math.random() * 29));
			String psw = "";
			for(int i=0; i<8; i++) {
				if(i%2 == 0) {
					psw += d.get();
				} else {
					psw += c.get();
				}
			}
			return psw;
		};
		System.out.println(s.get());
		System.out.println(s.get());
		System.out.println(s.get());
	}
}

Output :

9V3#4I7R
7I9Z2Q5$
8D8N0Z3A

. . . . .

Comparison Table of Predicate, Function, Consumer and Supplier :

Property	Predicate	Function	Consumer	Supplier
1. Purpose	To take some input and perform some conditional checks	To take some input and perform required operation and return the result	To consume some input and perform required operation. It won’t return anything	To supply some value base on our requirement
2. Interface Declaration	interface Predicate<T> { …. }	interface Function<T, R> { …. }	interface Consumer<T> { …. }	interface Supplier<R> { …. }
3. Signle Abstract Method (SAM)	public boolean test (T t);	public R apply (T t);	public void accept (T t);	public R get();
4. Default Methods	and(), or(), negate()	andThen(), compose()	andThen()	–
5. Static Method	isEqual()	identify()	–	–