Merge branch 'master' into readme-description-edits

2019-12-15 09:54:49 +00:00
parent 192450a258 f4420e8e99
commit 744e6e9f0d
316 changed files with 3708 additions and 859 deletions
@@ -0,0 +1,58 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-13</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-13</name>
+    <packaging>jar</packaging>
+    <url>http://maven.apache.org</url>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source.version}</source>
+                    <target>${maven.compiler.target.version}</target>
+                    <release>13</release>
+                    <compilerArgs>--enable-preview</compilerArgs>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.0.0-M3</version>
+                <configuration>
+                    <argLine>--enable-preview</argLine>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source.version>13</maven.compiler.source.version>
+        <maven.compiler.target.version>13</maven.compiler.target.version>
+        <assertj.version>3.6.1</assertj.version>
+    </properties>
+
+</project>
@@ -0,0 +1,76 @@
+package com.baeldung.switchExpression;
+
+import static java.time.Month.AUGUST;
+import static java.time.Month.JUNE;
+
+import static org.junit.Assert.assertEquals;
+
+import java.time.Month;
+import java.util.function.Function;
+
+import org.junit.Test;
+
+public class SwitchExpressionsUnitTest {
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthJune_thenWillReturn3() {
+
+    var month = JUNE;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL -> 2;
+      default -> 0;
+    };
+
+    assertEquals(result, 3);
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthAugust_thenWillReturn24() {
+    var month = AUGUST;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL, AUGUST -> {
+        int monthLength = month.toString().length();
+        yield monthLength * 4;
+      }
+      default -> 0;
+    };
+
+    assertEquals(24, result);
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthJanuary_thenWillReturn3() {
+
+    Function<Month, Integer> func = (month) -> {
+      switch (month) {
+        case JANUARY, JUNE, JULY -> { return 3; }
+        default -> { return 0; }
+      }
+    };
+
+    assertEquals(Integer.valueOf(3), func.apply(Month.JANUARY));
+  }
+
+  @Test
+  @SuppressWarnings ("preview")
+  public void whenSwitchingOverMonthAugust_thenWillReturn2() {
+    var month = AUGUST;
+
+    var result = switch (month) {
+      case JANUARY, JUNE, JULY -> 3;
+      case FEBRUARY, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER -> 1;
+      case MARCH, MAY, APRIL, AUGUST -> 2;
+    };
+
+    assertEquals(result, 2);
+  }
+}
@@ -6,4 +6,6 @@ This module contains articles about advanced topics about multithreading with co

 ### Relevant Articles: 

+- [Common Concurrency Pitfalls in Java](https://www.baeldung.com/java-common-concurrency-pitfalls)
+- [Guide to RejectedExecutionHandler](https://www.baeldung.com/java-rejectedexecutionhandler)
 [[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)
@@ -1,3 +1,8 @@
+## Core Date Operations
+This module contains articles about date operations in Java.
+
 ### Relevant Articles:
 - [Get the Current Date Prior to Java 8](https://www.baeldung.com/java-get-the-current-date-legacy)
 - [Skipping Weekends While Adding Days to LocalDate in Java 8](https://www.baeldung.com/java-localdate-add-days-skip-weekends)
+- [Checking If Two Java Dates Are on the Same Day](https://www.baeldung.com/java-check-two-dates-on-same-day)
+- [Converting Java Date to OffsetDateTime](https://www.baeldung.com/java-convert-date-to-offsetdatetime)
@@ -5,6 +5,7 @@
    <modelVersion>4.0.0</modelVersion>
    <artifactId>core-java-date-operations</artifactId>
    <version>${project.parent.version}</version>
+    <name>core-java-date-operations</name>
    <packaging>jar</packaging>

    <parent>
@@ -0,0 +1,19 @@
+package com.baeldung.offsetdatetime;
+
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+import java.util.Date;
+
+public class ConvertToOffsetDateTime {
+
+    public static OffsetDateTime convert(Date date) {
+        return date.toInstant()
+            .atOffset(ZoneOffset.UTC);
+    }
+
+    public static OffsetDateTime convert(Date date, int hour, int minute) {
+        return date.toInstant()
+            .atOffset(ZoneOffset.ofHoursMinutes(hour, minute));
+    }
+
+}
@@ -1,4 +1,4 @@
-package com.baeldung.datetime;
+package com.baeldung.skipweekends;

 import java.time.DayOfWeek;
 import java.time.LocalDate;
@@ -1,13 +1,13 @@
 package com.baeldung.date.comparison;

-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertTrue;
+import org.junit.Test;

 import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.util.Date;

-import org.junit.Test;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;

 public class DateComparisonUtilsUnitTest {

@@ -1,15 +1,12 @@
 package com.baeldung.datetime;

-import static org.junit.Assert.assertEquals;
-
 import org.junit.Test;

-import com.baeldung.datetime.CalendarUtils;
-import com.baeldung.datetime.DateUtils;
-
 import java.text.ParseException;
 import java.util.Date;

+import static org.junit.Assert.assertEquals;
+
 public class CalendarUtilsUnitTest {

    @Test
@@ -1,14 +1,12 @@
 package com.baeldung.datetime;

-import static org.junit.Assert.assertEquals;
-
 import org.junit.Test;

-import com.baeldung.datetime.DateUtils;
-
 import java.text.ParseException;
 import java.util.Date;

+import static org.junit.Assert.assertEquals;
+
 public class DateUtilsUnitTest {

    @Test
@@ -0,0 +1,29 @@
+package com.baeldung.offsetdatetime;
+
+import org.junit.Test;
+
+import java.time.OffsetDateTime;
+import java.util.Date;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ConvertToOffsetDateTimeUnitTest {
+
+    @Test
+    public void whenDateIsNotNull_thenConvertToOffsetDateTime() {
+        Date date = new Date();
+        assertTrue(ConvertToOffsetDateTime.convert(date) instanceof OffsetDateTime);
+    }
+
+    @Test
+    public void givenDate_whenHasOffset_thenConvertWithOffset() {
+        Date date = new Date();
+        date.setHours(6);
+        date.setMinutes(30);
+        OffsetDateTime odt = ConvertToOffsetDateTime.convert(date, 3, 30);
+        assertEquals(10, odt.getHour());
+        assertEquals(0, odt.getMinute());
+    }
+
+}
@@ -1,7 +1,8 @@
-package com.baeldung.datetime;
+package com.baeldung.skipweekends;

 import static org.junit.Assert.assertEquals;

+import com.baeldung.skipweekends.AddSubtractDaysSkippingWeekendsUtils;
 import org.junit.Test;

 import java.time.LocalDate;
@@ -0,0 +1,5 @@
+## Core Java Exceptions 2
+
+This module contains articles about core java exceptions
+
+###
@@ -0,0 +1,24 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+
+	<artifactId>core-java-exceptions-2</artifactId>
+	<name>core-java-exceptions-2</name>
+	<packaging>jar</packaging>
+
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-java</artifactId>
+		<version>0.0.1-SNAPSHOT</version>
+		<relativePath>../../parent-java</relativePath>
+	</parent>
+
+	<description> </description>
+	<url>http://maven.apache.org</url>
+
+	<properties>
+		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+	</properties>
+
+</project>
@@ -0,0 +1,29 @@
+package com.baeldung.rethrow;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+import com.baeldung.rethrow.custom.InvalidDataException;
+
+public class RethrowDifferentExceptionDemo {
+
+    private final static Logger LOGGER = Logger.getLogger(RethrowDifferentExceptionDemo.class.getName());
+
+    public static void main(String[] args) throws Exception {
+        String name = null;
+
+        try {
+
+            // Below line will throw NullPointerException
+            if (name.equals("Joe")) {
+                // Do blah blah..
+            }
+
+        } catch (Exception e) {
+            LOGGER.log(Level.WARNING, "So and so user is unable to cast vote because he is found uneligible");
+            throw new InvalidDataException(e);
+        }
+
+    }
+
+}
@@ -0,0 +1,27 @@
+package com.baeldung.rethrow;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class RethrowSameExceptionDemo {
+
+    private final static Logger LOGGER = Logger.getLogger(RethrowDifferentExceptionDemo.class.getName());
+
+    public static void main(String[] args) throws Exception {
+        String name = null;
+
+        try {
+
+            // Below line will throw NullPointerException
+            if (name.equals("Joe")) {
+                // Do blah blah..
+            }
+
+        } catch (Exception e) {
+            LOGGER.log(Level.WARNING, "Exception occurred due to invalid name");
+            throw e;
+        }
+
+    }
+
+}
@@ -0,0 +1,8 @@
+package com.baeldung.rethrow.custom;
+
+public class InvalidDataException extends Exception {
+
+    public InvalidDataException(Exception e) {
+        super(e);
+    }
+}
@@ -0,0 +1,34 @@
+package com.baeldung.exitvshalt;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class JvmExitAndHaltDemo {
+
+    private static Logger LOGGER = LoggerFactory.getLogger(JvmExitAndHaltDemo.class);
+
+    static {
+        Runtime.getRuntime()
+            .addShutdownHook(new Thread(() -> {
+                LOGGER.info("Shutdown hook initiated.");
+            }));
+    }
+
+    public void processAndExit() {
+        process();
+        LOGGER.info("Calling System.exit().");
+        System.exit(0);
+    }
+
+    public void processAndHalt() {
+        process();
+        LOGGER.info("Calling Runtime.getRuntime().halt().");
+        Runtime.getRuntime()
+            .halt(0);
+    }
+
+    private void process() {
+        LOGGER.info("Process started.");
+    }
+
+}
@@ -0,0 +1,14 @@
+package com.baeldung.exitvshalt;
+
+import org.junit.Test;
+
+public class JvmExitDemoUnitTest {
+
+    JvmExitAndHaltDemo jvmExitAndHaltDemo = new JvmExitAndHaltDemo();
+
+    @Test
+    public void givenProcessComplete_whenExitCalled_thenTriggerShutdownHook() {
+        jvmExitAndHaltDemo.processAndExit();
+    }
+
+}
@@ -0,0 +1,14 @@
+package com.baeldung.exitvshalt;
+
+import org.junit.Test;
+
+public class JvmHaltDemoUnitTest {
+
+    JvmExitAndHaltDemo jvmExitAndHaltDemo = new JvmExitAndHaltDemo();
+
+    @Test
+    public void givenProcessComplete_whenHaltCalled_thenDoNotTriggerShutdownHook() {
+        jvmExitAndHaltDemo.processAndHalt();
+    }
+
+}
@@ -0,0 +1,47 @@
+package com.baeldung.shutdownhook;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+public class ShutdownHookUnitTest {
+
+    @Test
+    public void givenAHook_WhenShutsDown_ThenHookShouldBeExecuted() {
+        Thread printingHook = new Thread(() -> System.out.println("In the middle of a shutdown"));
+        Runtime.getRuntime().addShutdownHook(printingHook);
+    }
+
+    @Test
+    public void addingAHook_WhenThreadAlreadyStarted_ThenThrowsAnException() {
+        Thread longRunningHook = new Thread(() -> {
+            try {
+                Thread.sleep(300);
+            } catch (InterruptedException ignored) {}
+        });
+        longRunningHook.start();
+
+        assertThatThrownBy(() -> Runtime.getRuntime().addShutdownHook(longRunningHook))
+          .isInstanceOf(IllegalArgumentException.class)
+          .hasMessage("Hook already running");
+    }
+
+    @Test
+    public void addingAHook_WhenAlreadyExists_ThenAnExceptionWouldBeThrown() {
+        Thread unfortunateHook = new Thread(() -> {});
+        Runtime.getRuntime().addShutdownHook(unfortunateHook);
+
+        assertThatThrownBy(() -> Runtime.getRuntime().addShutdownHook(unfortunateHook))
+          .isInstanceOf(IllegalArgumentException.class)
+          .hasMessage("Hook previously registered");
+    }
+
+    @Test
+    public void removeAHook_WhenItIsAlreadyRegistered_ThenWouldDeRegisterTheHook() {
+        Thread willNotRun = new Thread(() -> System.out.println("Won't run!"));
+        Runtime.getRuntime().addShutdownHook(willNotRun);
+
+        assertThat(Runtime.getRuntime().removeShutdownHook(willNotRun)).isTrue();
+    }
+}