Java BooleanSupplier
May 03, 2020
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();
}
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 instantiateBooleanSupplier 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());
}
}
true true true
Using Method Reference
Find the code to instantiateBooleanSupplier 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;
}
}
true false
Passing as Method Parameter
Here we will passBooleanSupplier 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";
}
}
Odd number --- With Stream.generate() --- true false true false true
