BAEL-6398: Java PrintStream to String (#13998)

core-java-modules/core-java-io-conversions-2/src/main/java/com/baeldung/printstreamtostring/PrintStreamToStringUtil.java

@@ -0,0 +1,68 @@
+package com.baeldung.printstreamtostring;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.PrintStream;
+
+public class PrintStreamToStringUtil {
+
+    public static String usingByteArrayOutputStreamClass(String input) throws IOException {
+        if (input == null) {
+            return null;
+        }
+
+        String output;
+        try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); PrintStream printStream = new PrintStream(outputStream)) {
+            printStream.print(input);
+
+            output = outputStream.toString();
+        }
+
+        return output;
+    }
+
+    public static String usingApacheCommonsIO(String input) {
+        if (input == null) {
+            return null;
+        }
+
+        org.apache.commons.io.output.ByteArrayOutputStream outputStream = new org.apache.commons.io.output.ByteArrayOutputStream();
+        try (PrintStream printStream = new PrintStream(outputStream)) {
+            printStream.print(input);
+        }
+
+        return new String(outputStream.toByteArray());
+    }
+
+    public static String usingCustomOutputStream(String input) throws IOException {
+        if (input == null) {
+            return null;
+        }
+
+        String output;
+        try (CustomOutputStream outputStream = new CustomOutputStream(); PrintStream printStream = new PrintStream(outputStream)) {
+            printStream.print(input);
+
+            output = outputStream.toString();
+        }
+
+        return output;
+    }
+
+    private static class CustomOutputStream extends OutputStream {
+
+        private StringBuilder stringBuilder = new StringBuilder();
+
+        @Override
+        public void write(int b) throws IOException {
+            this.stringBuilder.append((char) b);
+        }
+
+        @Override
+        public String toString() {
+            return this.stringBuilder.toString();
+        }
+    }
+
+}

core-java-modules/core-java-io-conversions-2/src/test/java/com/baeldung/printstreamtostring/PrintStreamToStringUtilUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.printstreamtostring;
+
+import static org.junit.Assert.assertNull;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+public class PrintStreamToStringUtilUnitTest {
+
+    @Test
+    public void whenUsingByteArrayOutputStreamClass_thenConvert() throws IOException {
+        assertEquals("test", PrintStreamToStringUtil.usingByteArrayOutputStreamClass("test"));
+        assertEquals("", PrintStreamToStringUtil.usingByteArrayOutputStreamClass(""));
+        assertNull(PrintStreamToStringUtil.usingByteArrayOutputStreamClass(null));
+    }
+
+    @Test
+    public void whenCustomOutputStream_thenConvert() throws IOException {
+        assertEquals("world", PrintStreamToStringUtil.usingCustomOutputStream("world"));
+        assertEquals("", PrintStreamToStringUtil.usingCustomOutputStream(""));
+        assertNull(PrintStreamToStringUtil.usingCustomOutputStream(null));
+    }
+
+    @Test
+    public void whenUsingApacheCommonsIO_thenConvert() {
+        assertEquals("hello", PrintStreamToStringUtil.usingApacheCommonsIO("hello"));
+        assertEquals("", PrintStreamToStringUtil.usingApacheCommonsIO(""));
+        assertNull(PrintStreamToStringUtil.usingApacheCommonsIO(null));
+    }
+}