Difference between two dates in java

java-difference-date/README.md

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+## Relevant articles:
+
+- [Constructor Dependency Injection in Spring](http://www.baeldung.com/constructor-injection-in-spring)

java-difference-date/pom.xml

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+<?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>java-difference-date</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<packaging>jar</packaging>
+
+	<name>java-difference-date</name>
+	<description>Difference between two dates in java</description>
+
+	<parent>
+		<groupId>com.baeldung</groupId>
+		<artifactId>parent-modules</artifactId>
+		<version>1.0.0-SNAPSHOT</version>
+	</parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>joda-time</groupId>
+            <artifactId>joda-time</artifactId>
+            <version>${joda-time.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.darwinsys</groupId>
+            <artifactId>hirondelle-date4j</artifactId>
+            <version>${hirondelle-date4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <target>1.8</target>
+                    <target>1.8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <java.version>1.8</java.version>
+        <junit.version>4.12</junit.version>
+        <joda-time.version>2.9.9</joda-time.version>
+        <hirondelle-date4j.version>1.5.1</hirondelle-date4j.version>
+    </properties>
+</project>

java-difference-date/src/main/java/com/baeldung/DateDiff.java

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+package com.baeldung;
+
+import org.joda.time.DateTime;
+
+import java.time.Duration;
+import java.time.ZonedDateTime;
+import java.util.Date;
+import java.util.concurrent.TimeUnit;
+
+public class DateDiff {
+    public long beforeJava8diff(Date firstDate, Date secondDate){
+        long diffInMillies = Math.abs(secondDate.getTime() - firstDate.getTime());
+        return TimeUnit.DAYS.convert(diffInMillies, TimeUnit.MILLISECONDS);
+    }
+
+    public long fromJava8Diff(ZonedDateTime firstDate, ZonedDateTime secondDate){
+        Duration duration = Duration.between(firstDate, secondDate);
+        return Math.abs(duration.toDays());
+    }
+
+    public long fromJodaTime(DateTime firstDate, DateTime secondDate){
+        org.joda.time.Duration duration = new org.joda.time.Duration(firstDate, secondDate);
+        return Math.abs(duration.getStandardDays());
+    }
+
+    public long fromDate4j(hirondelle.date4j.DateTime firstDate, hirondelle.date4j.DateTime secondDate){
+        long diff = firstDate.numDaysFrom(secondDate);
+        return Math.abs(diff);
+    }
+}

java-difference-date/src/test/java/com/baeldung/DateDiffTest.java

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+package com.baeldung;
+
+import org.joda.time.DateTime;
+import org.junit.Test;
+
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.time.ZonedDateTime;
+import java.util.Date;
+import java.util.Locale;
+import java.util.TimeZone;
+
+import static org.junit.Assert.assertEquals;
+
+public class DateDiffTest {
+    @Test
+    public void givenTwoDatesBeforeJava8SeparatedBySixDays_whenCallingDiffOnThem_thenWeGetSix() throws ParseException {
+        SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH);
+        Date firstDate = sdf.parse("06/24/2017");
+        Date secondDate = sdf.parse("06/30/2017");
+
+        DateDiff dateDiff = new DateDiff();
+        long diff = dateDiff.beforeJava8diff(firstDate, secondDate);
+
+        assertEquals(diff, 6);
+    }
+
+    @Test
+    public void givenTheCurrentDateAndSixDaysBehindInJava8_whenCallingDiffOnThem_thenWeGetSix() {
+        ZonedDateTime now = ZonedDateTime.now();
+        ZonedDateTime sixDaysBehind = now.minusDays(6);
+
+        DateDiff dateDiff = new DateDiff();
+        long diff = dateDiff.fromJava8Diff(now, sixDaysBehind);
+
+        assertEquals(diff, 6);
+    }
+
+    @Test
+    public void givenTheCurrentDateAndSixDaysBehindInJodaTime_whenCallingDiffOnThem_thenWeGetSix() {
+        DateTime now = DateTime.now();
+        DateTime sixDaysBehind = now.minusDays(6);
+
+        DateDiff dateDiff = new DateDiff();
+        long diff = dateDiff.fromJodaTime(now, sixDaysBehind);
+
+        assertEquals(diff, 6);
+    }
+
+    @Test
+    public void givenTheCurrentDateAndSixDaysBehindInDate4j_whenCallingDiffOnThem_thenWeGetSix() {
+        hirondelle.date4j.DateTime now = hirondelle.date4j.DateTime.now(TimeZone.getDefault());
+        hirondelle.date4j.DateTime sixDaysBehind = now.minusDays(6);
+
+        DateDiff dateDiff = new DateDiff();
+        long diff = dateDiff.fromDate4j(now, sixDaysBehind);
+
+        assertEquals(diff, 6);
+    }
+}

pom.xml

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         <module>immutables</module>
 
         <module>jackson</module>
+        <module>java-difference-date</module>
         <module>java-cassandra</module>
         <module>javaslang</module>
         <module>javax-servlets</module>