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 :