JAVA-23319 | Moving DualPrintStream (#14524)

* JAVA-23319 | moving DualPrintStream

* JAVA-23319 | adding checkerror

core-java-modules/core-java-io-apis/src/main/java/com/baeldung/outputtofile/DualPrintStream.java

@@ -0,0 +1,49 @@
+package com.baeldung.outputtofile;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+
+class DualPrintStream extends PrintStream {
+    private final PrintStream second;
+
+    public DualPrintStream(OutputStream main, PrintStream second) {
+        super(main);
+        this.second = second;
+    }
+
+    @Override
+    public void close() {
+        super.close();
+        second.close();
+    }
+
+    @Override
+    public void flush() {
+        super.flush();
+        second.flush();
+    }
+
+    @Override
+    public void write(byte[] buf, int off, int len) {
+        super.write(buf, off, len);
+        second.write(buf, off, len);
+    }
+
+    @Override
+    public void write(int b) {
+        super.write(b);
+        second.write(b);
+    }
+
+    @Override
+    public void write(byte[] b) throws IOException {
+        super.write(b);
+        second.write(b);
+    }
+
+    @Override
+    public boolean checkError() {
+        return super.checkError() && second.checkError();
+    }
+}

core-java-modules/core-java-io-apis/src/test/java/com/baeldung/outputtofile/ConsoleOutputToFileUnitTest.java

@@ -4,7 +4,6 @@ import static org.junit.jupiter.api.Assertions.assertLinesMatch;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.io.IOException;
-import java.io.OutputStream;
 import java.io.PrintStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
@@ -15,45 +14,6 @@ import org.junit.jupiter.api.io.TempDir;
 
 import com.google.common.collect.Lists;
 
-class DualPrintStream extends PrintStream {
-    private final PrintStream second;
-
-    public DualPrintStream(OutputStream main, PrintStream second) {
-        super(main);
-        this.second = second;
-    }
-
-    @Override
-    public void close() {
-        super.close();
-        second.close();
-    }
-
-    @Override
-    public void flush() {
-        super.flush();
-        second.flush();
-    }
-
-    @Override
-    public void write(byte[] buf, int off, int len) {
-        super.write(buf, off, len);
-        second.write(buf, off, len);
-    }
-
-    @Override
-    public void write(int b) {
-        super.write(b);
-        second.write(b);
-    }
-
-    @Override
-    public void write(byte[] b) throws IOException {
-        super.write(b);
-        second.write(b);
-    }
-}
-
 public class ConsoleOutputToFileUnitTest {
 
     // @formatter:off