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Java BooleanSupplier Example

By Arvind Rai, May 03, 2020
This page will walk through BooleanSupplier example. The BooleanSupplier is the functional interface introduced in Java 8 under the java.util.function package. The BooleanSupplier is the boolean-producing primitive specialization of Supplier functional interface. The functional method of BooleanSupplier is getAsBoolean() which returns Boolean result. Find the BooleanSupplier structure from Java doc.
@FunctionalInterface
public interface BooleanSupplier {
    boolean getAsBoolean();
} 
The BooleanSupplier can be instantiated using lambda expression and method reference.
Here we will provide using BooleanSupplier in our applications in detail.

Using Lambda Expression

Find the code to instantiate BooleanSupplier using lambda expression.
BooleanSupplierWithLE.java
package com.concretepage;
import java.time.LocalDate;
import java.util.function.BooleanSupplier;
public class BooleanSupplierWithLE {
  public static void main(String[] args) {
      BooleanSupplier dt = () -> LocalDate.now().isLeapYear();
      System.out.println(dt.getAsBoolean());

      BooleanSupplier bs = () ->  "my_username".length() > 5;
      System.out.println(bs.getAsBoolean());      
      
      BooleanSupplier evenBs = () -> {
    	int num = 16;
    	if (num % 2 == 0) {
    	  return true;
    	}
    	return false;
      };
      System.out.println(evenBs.getAsBoolean());  
  }
} 
Output
true
true
true 

Using Method Reference

Find the code to instantiate BooleanSupplier using method reference.
BooleanSupplierWithMR.java
package com.concretepage;
import java.util.function.BooleanSupplier;
public class BooleanSupplierWithMR {
  public static void main(String[] args) {
	BooleanSupplier bs1 = AppUtil::isDataBaseUp;
	System.out.println(bs1.getAsBoolean());

	BooleanSupplier bs2 = AppUtil::isInternetUp;
	System.out.println(bs2.getAsBoolean());	
  }
}

class AppUtil {
  public static boolean isDataBaseUp() {
	return true;
  }
  public static boolean isInternetUp() {
	return false;
  }
} 
Output
true
false 

Passing as Method Parameter

Here we will pass BooleanSupplier as method parameter.
WithMethodParameter.java
package com.concretepage;
import java.util.Random;
import java.util.function.BooleanSupplier;
import java.util.stream.Stream;
public class WithMethodParameter {
  public static void main(String[] args) {
	int num = 11;
	String msg = getMsg(() -> num % 2 == 1);
	System.out.println(msg);

	System.out.println("--- With Stream.generate() ---");
	Stream<Boolean> stream = Stream.generate(() -> new Random().nextBoolean()).limit(5);
	stream.forEach(b -> System.out.println(b));
  }

  static String getMsg(BooleanSupplier oddBs) {
	if (oddBs.getAsBoolean()) {
	  return "Odd number";
	}
	return "Even number";
  }
} 
Output
Odd number
--- With Stream.generate() ---
true
false
true
false
true 

Reference

Java doc: BooleanSupplier
POSTED BY
ARVIND RAI
ARVIND RAI








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