core-java-lambdas 项目添加

2024-04-30 09:21:11 -04:00
parent 0d46c069be
commit afc5ab001b
29 changed files with 1364 additions and 0 deletions
@@ -0,0 +1,85 @@
+package com.baeldung.doublecolon;
+
+public class Computer {
+
+    private Integer age;
+    private String color;
+    private Integer healty;
+
+    Computer(final int age, final String color) {
+        this.age = age;
+        this.color = color;
+    }
+
+    Computer(final Integer age, final String color, final Integer healty) {
+        this.age = age;
+        this.color = color;
+        this.healty = healty;
+    }
+
+    public Computer() {
+    }
+
+    public Integer getAge() {
+        return age;
+    }
+
+    public void setAge(final Integer age) {
+        this.age = age;
+    }
+
+    String getColor() {
+        return color;
+    }
+
+    public void setColor(final String color) {
+        this.color = color;
+    }
+
+    Integer getHealty() {
+        return healty;
+    }
+
+    void setHealty(final Integer healty) {
+        this.healty = healty;
+    }
+
+    public void turnOnPc() {
+        System.out.println("Computer turned on");
+    }
+
+    public void turnOffPc() {
+        System.out.println("Computer turned off");
+    }
+
+    public Double calculateValue(Double initialValue) {
+        return initialValue / 1.50;
+    }
+
+    @Override
+    public String toString() {
+        return "Computer{" + "age=" + age + ", color='" + color + '\'' + ", healty=" + healty + '}';
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        final Computer computer = (Computer) o;
+
+        return (age != null ? age.equals(computer.age) : computer.age == null) && (color != null ? color.equals(computer.color) : computer.color == null);
+
+    }
+
+    @Override
+    public int hashCode() {
+        int result = age != null ? age.hashCode() : 0;
+        result = 31 * result + (color != null ? color.hashCode() : 0);
+        return result;
+    }
+}
@@ -0,0 +1,27 @@
+package com.baeldung.doublecolon;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.baeldung.doublecolon.function.ComputerPredicate;
+
+public class ComputerUtils {
+
+    static final ComputerPredicate after2010Predicate = (c) -> (c.getAge() > 2010);
+    static final ComputerPredicate blackPredicate = (c) -> "black".equals(c.getColor());
+
+    public static List<Computer> filter(final List<Computer> inventory, final ComputerPredicate p) {
+
+        final List<Computer> result = new ArrayList<>();
+        inventory.stream().filter(p::filter).forEach(result::add);
+
+        return result;
+    }
+
+    static void repair(final Computer computer) {
+        if (computer.getHealty() < 50) {
+            computer.setHealty(100);
+        }
+    }
+
+}
@@ -0,0 +1,39 @@
+package com.baeldung.doublecolon;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.function.Function;
+
+public class MacbookPro extends Computer {
+
+    private static final Logger LOG = LoggerFactory.getLogger(MacbookPro.class);
+
+    public MacbookPro(int age, String color) {
+        super(age, color);
+    }
+
+    MacbookPro(Integer age, String color, Integer healty) {
+        super(age, color, healty);
+    }
+
+    @Override
+    public void turnOnPc() {
+        LOG.debug("MacbookPro turned on");
+    }
+
+    @Override
+    public void turnOffPc() {
+        LOG.debug("MacbookPro turned off");
+    }
+
+    @Override
+    public Double calculateValue(Double initialValue) {
+
+        Function<Double, Double> function = super::calculateValue;
+        final Double pcValue = function.apply(initialValue);
+        LOG.debug("First value is:" + pcValue);
+        return pcValue + (initialValue / 10);
+
+    }
+}
@@ -0,0 +1,10 @@
+package com.baeldung.doublecolon.function;
+
+import com.baeldung.doublecolon.Computer;
+
+@FunctionalInterface
+public interface ComputerPredicate {
+
+    boolean filter(Computer c);
+
+}
@@ -0,0 +1,15 @@
+package com.baeldung.doublecolon.function;
+
+import java.util.Objects;
+import java.util.function.Function;
+
+@FunctionalInterface
+public interface TriFunction<A, B, C, R> {
+
+    R apply(A a, B b, C c);
+
+    default <V> TriFunction<A, B, C, V> andThen(final Function<? super R, ? extends V> after) {
+        Objects.requireNonNull(after);
+        return (final A a, final B b, final C c) -> after.apply(apply(a, b, c));
+    }
+}
@@ -0,0 +1,89 @@
+package com.baeldung.java8.entity;
+
+public class Human {
+    private String name;
+    private int age;
+
+    public Human() {
+        super();
+    }
+
+    public Human(final String name, final int age) {
+        super();
+
+        this.name = name;
+        this.age = age;
+    }
+
+    // API
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(final String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(final int age) {
+        this.age = age;
+    }
+
+    // compare
+
+    public static int compareByNameThenAge(final Human lhs, final Human rhs) {
+        if (lhs.name.equals(rhs.name)) {
+            return Integer.compare(lhs.age, rhs.age);
+        } else {
+            return lhs.name.compareTo(rhs.name);
+        }
+    }
+
+    //
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + age;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(final Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null) {
+            return false;
+        }
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+        final Human other = (Human) obj;
+        if (age != other.age) {
+            return false;
+        }
+        if (name == null) {
+            if (other.name != null) {
+                return false;
+            }
+        } else if (!name.equals(other.name)) {
+            return false;
+        }
+        return true;
+    }
+
+    @Override
+    public String toString() {
+        final StringBuilder builder = new StringBuilder();
+        builder.append("Human [name=").append(name).append(", age=").append(age).append("]");
+        return builder.toString();
+    }
+
+}
@@ -0,0 +1,62 @@
+package com.baeldung.java8.lambda.exceptions;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.function.Consumer;
+
+public class LambdaExceptionWrappers {
+
+    private static final Logger LOGGER = LoggerFactory.getLogger(LambdaExceptionWrappers.class);
+
+    public static Consumer<Integer> lambdaWrapper(Consumer<Integer> consumer) {
+        return i -> {
+            try {
+                consumer.accept(i);
+            } catch (ArithmeticException e) {
+                LOGGER.error("Arithmetic Exception occurred.", e);
+            }
+        };
+    }
+
+    static <T, E extends Exception> Consumer<T> consumerWrapper(Consumer<T> consumer, Class<E> clazz) {
+        return i -> {
+            try {
+                consumer.accept(i);
+            } catch (Exception ex) {
+                try {
+                    E exCast = clazz.cast(ex);
+                    LOGGER.error("Exception occurred.", exCast);
+                } catch (ClassCastException ccEx) {
+                    throw ex;
+                }
+            }
+        };
+    }
+
+    public static <T> Consumer<T> throwingConsumerWrapper(ThrowingConsumer<T, Exception> throwingConsumer) {
+        return i -> {
+            try {
+                throwingConsumer.accept(i);
+            } catch (Exception ex) {
+                throw new RuntimeException(ex);
+            }
+        };
+    }
+
+    public static <T, E extends Exception> Consumer<T> handlingConsumerWrapper(ThrowingConsumer<T, E> throwingConsumer, Class<E> exceptionClass) {
+        return i -> {
+            try {
+                throwingConsumer.accept(i);
+            } catch (Exception ex) {
+                try {
+                    E exCast = exceptionClass.cast(ex);
+                    LOGGER.error("Exception occurred.", exCast);
+                } catch (ClassCastException ccEx) {
+                    throw new RuntimeException(ex);
+                }
+            }
+        };
+    }
+
+}
@@ -0,0 +1,8 @@
+package com.baeldung.java8.lambda.exceptions;
+
+@FunctionalInterface
+public interface ThrowingConsumer<T, E extends Exception> {
+
+    void accept(T t) throws E;
+
+}
@@ -0,0 +1,16 @@
+package com.baeldung.java8.lambda.tips;
+
+
+@FunctionalInterface
+public interface Bar {
+
+    String method(String string);
+
+    default String defaultBar() {
+        return "Default String from Bar";
+    }
+
+    default String defaultCommon() {
+        return "Default Common from Bar";
+    }
+}
@@ -0,0 +1,16 @@
+package com.baeldung.java8.lambda.tips;
+
+
+@FunctionalInterface
+public interface Baz {
+
+    String method(String string);
+
+    default String defaultBaz() {
+        return "Default String from Baz";
+    }
+
+    default String defaultCommon(){
+        return "Default Common from Baz";
+    }
+}
@@ -0,0 +1,11 @@
+package com.baeldung.java8.lambda.tips;
+
+
+@FunctionalInterface
+public interface Foo {
+
+    String method(String string);
+
+    default void defaultMethod() {
+    }
+}
@@ -0,0 +1,11 @@
+package com.baeldung.java8.lambda.tips;
+
+
+@FunctionalInterface
+public interface FooExtended extends Baz, Bar {
+
+    @Override
+    default String defaultCommon() {
+        return Bar.super.defaultCommon();
+    }
+}
@@ -0,0 +1,12 @@
+package com.baeldung.java8.lambda.tips;
+
+import java.util.concurrent.Callable;
+import java.util.function.Supplier;
+
+public interface Processor {
+
+    String processWithCallable(Callable<String> c) throws Exception;
+
+    String processWithSupplier(Supplier<String> s);
+
+}
@@ -0,0 +1,20 @@
+package com.baeldung.java8.lambda.tips;
+
+
+import java.util.concurrent.Callable;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class ProcessorImpl implements Processor {
+
+    @Override
+    public String processWithCallable(Callable<String> c) throws Exception {
+        return c.call();
+    }
+
+    @Override
+    public String processWithSupplier(Supplier<String> s) {
+        return s.get();
+    }
+}
@@ -0,0 +1,38 @@
+package com.baeldung.java8.lambda.tips;
+
+
+import java.util.function.Function;
+
+public class UseFoo {
+
+    private String value = "Enclosing scope value";
+
+    public String add(final String string, final Foo foo) {
+        return foo.method(string);
+    }
+
+    public String addWithStandardFI(final String string, final Function<String, String> fn) {
+        return fn.apply(string);
+    }
+
+    public String scopeExperiment() {
+        final Foo fooIC = new Foo() {
+            String value = "Inner class value";
+
+            @Override
+            public String method(final String string) {
+                return value;
+            }
+        };
+        final String resultIC = fooIC.method("");
+
+        final Foo fooLambda = parameter -> {
+            final String value = "Lambda value";
+            return this.value;
+        };
+        final String resultLambda = fooLambda.method("");
+
+        return "Results: resultIC = " + resultIC + ", resultLambda = " + resultLambda;
+    }
+
+}
@@ -0,0 +1,88 @@
+package com.baeldung.lambdas;
+
+import java.util.Random;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Supplier;
+import java.util.stream.IntStream;
+
+/**
+ * Class with examples about working with capturing lambdas.
+ */
+public class LambdaVariables {
+
+    private volatile boolean run = true;
+    private int start = 0;
+
+    private ExecutorService executor = Executors.newFixedThreadPool(3);
+
+    public static void main(String[] args) {
+        new LambdaVariables().localVariableMultithreading();
+    }
+
+    Supplier<Integer> incrementer(int start) {
+        return () -> start; // can't modify start parameter inside the lambda
+    }
+
+    Supplier<Integer> incrementer() {
+        return () -> start++;
+    }
+
+    public void localVariableMultithreading() {
+        boolean run = true;
+        executor.execute(() -> {
+            while (run) {
+                // do operation
+            }
+        });
+        // commented because it doesn't compile, it's just an example of non-final local variables in lambdas
+        // run = false;
+    }
+
+    public void instanceVariableMultithreading() {
+        executor.execute(() -> {
+            while (run) {
+                // do operation
+            }
+        });
+
+        run = false;
+    }
+
+    /**
+     * WARNING: always avoid this workaround!!
+     */
+    public void workaroundSingleThread() {
+        int[] holder = new int[] { 2 };
+        IntStream sums = IntStream
+          .of(1, 2, 3)
+          .map(val -> val + holder[0]);
+
+        holder[0] = 0;
+
+        System.out.println(sums.sum());
+    }
+
+    /**
+     * WARNING: always avoid this workaround!!
+     */
+    public void workaroundMultithreading() {
+        int[] holder = new int[] { 2 };
+        Runnable runnable = () -> System.out.println(IntStream
+          .of(1, 2, 3)
+          .map(val -> val + holder[0])
+          .sum());
+
+        new Thread(runnable).start();
+
+        // simulating some processing
+        try {
+            Thread.sleep(new Random().nextInt(3) * 1000L);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+
+        holder[0] = 0;
+    }
+
+}
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>