BAEL-821 - How to round a number to n decimal places in Java (#1953)

* Code for Dependency Injection Article.

* Added Java based configuration. Downloaded formatter.xml and reformatted
all changed files. Manually changed tab into 4 spaces in XML
configuration files.

* BAEL-434 - Spring Roo project files generated by Spring Roo. No
formatting applied. Added POM, java and resources folders.

* Moved project from roo to spring-roo folder.

* BAEL-838 Initial code showing how to remove last char - helper class and tests.

* BAEL-838 Corrected Helper class and associated empty string test case. Added StringUtils.substing tests.

* BAEL-838 Refromatted code using formatter.xml. Added Assert.assertEquals import. Renamed test to follow convention. Reordered tests.

* BAEL-838 - Added regex method and updated tests.

* BAEL-838 Added new line examples.

* BAEL-838 Renamed RemoveLastChar class to StringHelper and added Java8 examples. Refactord code.

* BAEL-838 Changed method names

* BAEL-838 Tiny change to keep code consistant. Return null or empty.

* BAEL-838 Removed unresolved conflict.

* BAEL-821 New class that shows different rounding techniques. Updated POM.

* BAEL-821 - Added unit test for different round methods.

* BAEL-821 Changed test method name to follow the convention

core-java/src/test/java/com/baeldung/maths/RoundTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.maths;
+
+import org.apache.commons.math3.util.Precision;
+import org.decimal4j.util.DoubleRounder;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class RoundTest {
+    private double value = 2.03456d;
+    private int places = 2;
+    private double delta = 0.0d;
+    private double expected = 2.03d;
+
+    @Test
+    public void givenDecimalNumber_whenRoundToNDecimalPlaces_thenGetExpectedResult() {   
+        Assert.assertEquals(expected, Round.round(value, places), delta);
+        Assert.assertEquals(expected, Round.roundOptional(value, places), delta);
+        Assert.assertEquals(expected, Precision.round(value, places), delta);
+        Assert.assertEquals(expected, DoubleRounder.round(value, places), delta);
+        
+        places = 3;
+        expected = 2.035d;
+        
+        Assert.assertEquals(expected, Round.round(value, places), delta);
+        Assert.assertEquals(expected, Round.roundOptional(value, places), delta);
+        Assert.assertEquals(expected, Precision.round(value, places), delta);
+        Assert.assertEquals(expected, DoubleRounder.round(value, places), delta);
+    }
+}