BAEL-5147 : convert ByteBuffer to String (#11504)

* BAEL-5147: convert ByteBuffer to String

* Update README.md

core-java-modules/core-java-string-conversions-2/README.md

@@ -9,4 +9,5 @@ This module contains articles about string conversions from/to another type.
 - [Converting String to BigDecimal in Java](https://www.baeldung.com/java-string-to-bigdecimal)
 - [Converting String to BigInteger in Java](https://www.baeldung.com/java-string-to-biginteger)
 - [Convert a String to Camel Case](https://www.baeldung.com/java-string-to-camel-case)
+- [Convert a ByteBuffer to String]
 - More articles: [[<-- prev]](/core-java-string-conversions)

core-java-modules/core-java-string-conversions-2/src/test/java/com/baeldung/bytebuffertostring/ByteArrayToStringUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.bytebuffertostring;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
+import org.junit.Test;
+
+public class ByteArrayToStringUnitTest {
+    private static Charset charset = StandardCharsets.UTF_8;
+    private static final String content = "baeldung";
+
+    @Test
+    public void convertUsingNewStringFromBufferArray_thenOK() {
+        // Allocate a ByteBuffer
+        ByteBuffer byteBuffer = ByteBuffer.wrap(content.getBytes());
+        if (byteBuffer.hasArray()) {
+            String newContent = new String(byteBuffer.array(), charset);
+            assertEquals(content, newContent);
+        }
+    }
+
+    @Test
+    public void convertUsingNewStringFromByteBufferGetBytes_thenOK() {
+        // Allocate a ByteBuffer
+        ByteBuffer byteBuffer = ByteBuffer.wrap(content.getBytes());
+        byte[] bytes = new byte[byteBuffer.remaining()];
+        byteBuffer.get(bytes);
+        String newContent = new String(bytes, charset);
+        assertEquals(content, newContent);
+    }
+
+    @Test
+    public void convertUsingCharsetDecode_thenOK() {
+        // Allocate a ByteBuffer
+        ByteBuffer byteBuffer = ByteBuffer.wrap(content.getBytes());
+        String newContent = charset.decode(byteBuffer)
+            .toString();
+        assertEquals(content, newContent);
+    }
+
+}