Loading a long value into a String variable from a text file

The max length of a string seems to equal Integer.MAX_VALUE. However, a string literal length in Java is represented by two bytes implying that it cannot be over 65535 bytes. If you try to compile a class with a longer string, an error constant string too long will occur. Sometimes, for example for tests, one needs to use longer String values. Such values can be loaded from a file.

Suppose, a String variable has to be assigned the entire contents of a output.xml file, which contains ~400,000 characters and is saved in the classpath. Method inputStreamToString loads the contents from an InputStream into a String variable:

public class FileUtils {

    public String inputStreamToString(InputStream is) throws IOException {
        StringBuilder sb = new StringBuilder();
        char[] buffer = new char[1024 * 8];
        try (BufferedReader in = new BufferedReader(new InputStreamReader(is, StandardCharsets.UTF_8))) {
            int length;
            while ((length = in.read(buffer)) > -1) {
                sb.append(buffer, 0, length);
            }
        }
        return sb.toString();
    }
}

A test class:

public class FileUtilsTest {

    FileUtils i = new FileUtils();

    @Test
    public void testInputStreamToStringFromResourceFile() throws IOException {
        String resp = i.inputStreamToString(getClass().getResourceAsStream("/output.xml"));
        System.out.println(resp.length());// 358,830
        assertEquals(resp.length(), 358779);
    }

    @Test
    public void testInputStreamToStringFromString() throws IOException {
        System.out.println(Charset.defaultCharset()); // windows-1252
        String str = "this is a test string to be converted to InputStream";
        String copy = i.inputStreamToString(new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8)));
        assertEquals(str.length(), copy.length());
    }
}

Another sorter possibility:

    public String readFileToString(String fileName) throws IOException {
        Path filePath = getPathInResources(fileName);
        return new String(Files.readAllBytes(filePath), StandardCharsets.UTF_8);
    }

How to convert a String to an InputStream

InputStream is=new ByteArrayInputStream(str.getBytes(StandardCharsets.UTF_8));

The code is used in the second test above.

How to save a String to a file

 Files.write(Paths.get("src\\test\\resources\\xml0.xml"),str.getBytes(StandardCharsets.UTF_8));