BAEL-7286 Print a double value without scientific notation in Java (#15427)

* BAEL-7051 - Catch Common Mistakes with Error-Prone Library in Java

* BAEL-7286
Print a double value without scientific notation in Java

* BAEL-7286
Print a double value without scientific notation in Java

* BAEL-7286 Print a double value without scientific notation in Java

* rename package

* format code

core-java-modules/core-java-numbers-7/src/test/java/com/baeldung/withoutscientificnotation/PrintDoubleWithoutScientificNotationUnitTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.withoutscientificnotation;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.math.BigDecimal;
+import java.text.DecimalFormat;
+import java.util.Locale;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class PrintDoubleWithoutScientificNotationUnitTest {
+
+    private final PrintStream standardOut = System.out;
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+        Locale.setDefault(Locale.US);
+    }
+
+    @AfterEach
+    public void tearDown() {
+        System.setOut(standardOut);
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithDecimalFormat_thenOutputIsWithoutScientificNotation() {
+
+        DecimalFormat df = new DecimalFormat("#.###########");
+        double largeNumber = 256450000d;
+        System.out.println("Large Number: " + df.format(largeNumber));
+
+        Assertions.assertEquals("Large Number: 256450000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithDecimalFormat_thenOutputIsWithoutScientificNotation() {
+
+        DecimalFormat df = new DecimalFormat("#.###########");
+        double smallNumber = 0.0000046d;
+        System.out.println("Small Number: " + df.format(smallNumber));
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithPrintf_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        System.out.printf("Large Number: %.7f", largeNumber);
+
+        Assertions.assertEquals("Large Number: 256450000.0000000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithPrintf_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        System.out.printf("Small Number: %.7f", smallNumber);
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithBigDecimal_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        System.out.println("Large Number: " + BigDecimal.valueOf(largeNumber).toPlainString());
+
+        Assertions.assertEquals("Large Number: 256450000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithBigDecimal_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        System.out.println("Small Number: " + BigDecimal.valueOf(smallNumber).toPlainString());
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenLargeNumber_whenPrintWithStringFormat_thenOutputIsWithoutScientificNotation() {
+
+        double largeNumber = 256450000d;
+        String formattedLargeNumber = String.format("%.7f", largeNumber);
+        System.out.println("Large Number: " + formattedLargeNumber);
+
+        Assertions.assertEquals("Large Number: 256450000.0000000", outputStreamCaptor.toString()
+          .trim());
+    }
+
+    @Test
+    void givenSmallNumber_whenPrintWithStringFormat_thenOutputIsWithoutScientificNotation() {
+
+        double smallNumber = 0.0000046d;
+        String formattedSmallNumber = String.format("%.7f", smallNumber);
+        System.out.println("Small Number: " + formattedSmallNumber);
+
+        Assertions.assertEquals("Small Number: 0.0000046", outputStreamCaptor.toString()
+          .trim());
+    }
+}