A class in Java is defined by the class keyword and for beginners, to get a better understanding, in this tutorial I will present the basic knowledge about the structure and its components in possible detail First of all, let’s say a Java class consists… Read More
The volatile variable in Java has the effect of informing the change of its value to different threads if the variable is being used in multiple threads. For you to understand more, I made an example as follows:
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public class VolatileExample { private volatile static int COUNT = 0; public static void main(String[] args) { new ChangeListener().start(); new ChangeMaker().start(); } static class ChangeListener extends Thread { @Override public void run() { int value = COUNT; // When value of COUNT variable is less than 5, this thread will loop forever to check the value of this variable while (value < 5) { if (value != COUNT) { System.out.println("Count variable changed to : " + COUNT); value = COUNT; } } } } static class ChangeMaker extends Thread { @Override public void run() { int value = COUNT; while (COUNT < 5) { System.out.println("Increasing value of count variable to " + (value + 1)); COUNT = ++value; try { Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); } } } } } |
In this example, we have two… Read More
In the previous tutorial, you learned some ways to initialize a String object in Java as well as the differences between them, and you also learned how String implements the Immutable concept. In this tutorial, I will continue to present to you all the basic… Read More
The String object, defined in the java.lang package, is a basic object in Java. You will use it often and it is an indispensable object for all of us when programming with Java. In this tutorial, I will present to you more depth on this… Read More
I have introduced to you about Type Inference in Java in the previous tutorial. If you have read it, you will probably know that this is a feature of the Java Compiler based on how the declaration, the call to determine the type of data without… Read More
Type Inference in Java is a Java Compiler’s ability base on the declaration, the calling to determine the datatype, without explicitly declaring it, reducing redundancy code. For you to understand more, I will take an example as follows. Assuming you are working with the List… Read More
In Java, variables, which are declared with the static keyword, belong to the class, not to the instance of the class. This means that we do not need to initialize objects to use variables that are declared with the static keyword in those classes. For… Read More
The Predicate interface is used primarily to filter a Stream object. Using the filter() method with the Predicate interface parameter will allow us to filter the items in the Stream object to satisfy some conditions. The content of this interface is as follows:
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/* * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.util.function; import java.util.Objects; /** * Represents a predicate (boolean-valued function) of one argument. * * <p>This is a <a href="package-summary.html">functional interface</a> * whose functional method is {@link #test(Object)}. * * @param <T> the type of the input to the predicate * * @since 1.8 */ @FunctionalInterface public interface Predicate<T> { /** * Evaluates this predicate on the given argument. * * @param t the input argument * @return {@code true} if the input argument matches the predicate, * otherwise {@code false} */ boolean test(T t); /** * Returns a composed predicate that represents a short-circuiting logical * AND of this predicate and another. When evaluating the composed * predicate, if this predicate is {@code false}, then the {@code other} * predicate is not evaluated. * * <p>Any exceptions thrown during evaluation of either predicate are relayed * to the caller; if evaluation of this predicate throws an exception, the * {@code other} predicate will not be evaluated. * * @param other a predicate that will be logically-ANDed with this * predicate * @return a composed predicate that represents the short-circuiting logical * AND of this predicate and the {@code other} predicate * @throws NullPointerException if other is null */ default Predicate<T> and(Predicate<? super T> other) { Objects.requireNonNull(other); return (t) -> test(t) && other.test(t); } /** * Returns a predicate that represents the logical negation of this * predicate. * * @return a predicate that represents the logical negation of this * predicate */ default Predicate<T> negate() { return (t) -> !test(t); } /** * Returns a composed predicate that represents a short-circuiting logical * OR of this predicate and another. When evaluating the composed * predicate, if this predicate is {@code true}, then the {@code other} * predicate is not evaluated. * * <p>Any exceptions thrown during evaluation of either predicate are relayed * to the caller; if evaluation of this predicate throws an exception, the * {@code other} predicate will not be evaluated. * * @param other a predicate that will be logically-ORed with this * predicate * @return a composed predicate that represents the short-circuiting logical * OR of this predicate and the {@code other} predicate * @throws NullPointerException if other is null */ default Predicate<T> or(Predicate<? super T> other) { Objects.requireNonNull(other); return (t) -> test(t) || other.test(t); } /** * Returns a predicate that tests if two arguments are equal according * to {@link Objects#equals(Object, Object)}. * * @param <T> the type of arguments to the predicate * @param targetRef the object reference with which to compare for equality, * which may be {@code null} * @return a predicate that tests if two arguments are equal according * to {@link Objects#equals(Object, Object)} */ static <T> Predicate<T> isEqual(Object targetRef) { return (null == targetRef) ? Objects::isNull : object -> targetRef.equals(object); } /** * Returns a predicate that is the negation of the supplied predicate. * This is accomplished by returning result of the calling * {@code target.negate()}. * * @param <T> the type of arguments to the specified predicate * @param target predicate to negate * * @return a predicate that negates the results of the supplied * predicate * * @throws NullPointerException if target is null * * @since 11 */ @SuppressWarnings("unchecked") static <T> Predicate<T> not(Predicate<? super T> target) { Objects.requireNonNull(target); return (Predicate<T>)target.negate(); } } |
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Everyone who has been and will be working on the Java language will know the concepts of JDK, JRE and JVM. So do people know what they are and the difference between them? In this tutorial, I will make clear to everyone to have a… Read More
Function interface is used to convert data from input parameters to return results in a different format. To do this, we will implement the apply() abstract method defined in the Function interface. But first, let’s look at the contents of the Function interface.
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package java.util.function; import java.util.Objects; /** * Represents a function that accepts one argument and produces a result. * * <p>This is a <a href="package-summary.html">functional interface</a> * whose functional method is {@link #apply(Object)}. * * @param <T> the type of the input to the function * @param <R> the type of the result of the function * * @since 1.8 */ @FunctionalInterface public interface Function<T, R> { /** * Applies this function to the given argument. * * @param t the function argument * @return the function result */ R apply(T t); /** * Returns a composed function that first applies the {@code before} * function to its input, and then applies this function to the result. * If evaluation of either function throws an exception, it is relayed to * the caller of the composed function. * * @param <V> the type of input to the {@code before} function, and to the * composed function * @param before the function to apply before this function is applied * @return a composed function that first applies the {@code before} * function and then applies this function * @throws NullPointerException if before is null * * @see #andThen(Function) */ default <V> Function<V, R> compose(Function<? super V, ? extends T> before) { Objects.requireNonNull(before); return (V v) -> apply(before.apply(v)); } /** * Returns a composed function that first applies this function to * its input, and then applies the {@code after} function to the result. * If evaluation of either function throws an exception, it is relayed to * the caller of the composed function. * * @param <V> the type of output of the {@code after} function, and of the * composed function * @param after the function to apply after this function is applied * @return a composed function that first applies this function and then * applies the {@code after} function * @throws NullPointerException if after is null * * @see #compose(Function) */ default <V> Function<T, V> andThen(Function<? super R, ? extends V> after) { Objects.requireNonNull(after); return (T t) -> after.apply(apply(t)); } /** * Returns a function that always returns its input argument. * * @param <T> the type of the input and output objects to the function * @return a function that always returns its input argument */ static <T> Function<T, T> identity() { return t -> t; } } |
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