javaTempfile.java

    try {
        // Create temp file.
        File temp = File.createTempFile("pattern", ".suffix");

        // Delete temp file when program exits.
        temp.deleteOnExit();

        // Write to temp file
        BufferedWriter out = new BufferedWriter(new FileWriter(temp));
        out.write("aString");
        out.close();
    } catch (IOException e) {
    }

Old code snippet for Java, the equivalent of shell mktemp