PreparedStatements are the way to go, because they make SQL injection impossible. Here's a simple example taking the user's input as the parameters:

public insertUser(String name, String email) {
   Connection conn = null;
   PreparedStatement stmt = null;
   try {
      conn = setupTheDatabaseConnectionSomehow();
      stmt = conn.prepareStatement("INSERT INTO person (name, email) values (?, ?)");
      stmt.setString(1, name);
      stmt.setString(2, email);
      stmt.executeUpdate();
   }
   finally {
      try {
         if (stmt != null) { stmt.close(); }
      }
      catch (Exception e) {
         // log this error
      }
      try {
         if (conn != null) { conn.close(); }
      }
      catch (Exception e) {
         // log this error
      }
   }
}

No matter what characters are in name and email, those characters will be placed directly in the database. They won't affect the INSERT statement in any way.

There are different set methods for different data types -- which one you use depends on what your database fields are. For example, if you have an INTEGER column in the database, you should use a setInt method. The PreparedStatement documentation lists all the different methods available for setting and getting data.

Right, prepared statement query parameters can be used only where you would use a single literal value. You can't use a parameter for a table name, a column name, a list of values, or any other SQL syntax.

So you have to interpolate your application variable into the SQL string and quote the string appropriately. Do use quoting to delimit your table name identifier, and escape the quote string by doubling it:

java.sql.DatabaseMetaData md = conn.getMetaData();
String q = md.getIdentifierQuoteString();
String sql = "SELECT MAX(AGE) FROM %s%s%s";
sql = String.format(sql, q, tablename.replaceAll(q, q+q), q);

For example, if your table name is literally table"name, and your RDBMS identifier quote character is ", then sql should contain a string like:

SELECT MAX(AGE) FROM "table""name"

I also agree with @ChssPly76's comment -- it's best if your user input is actually not the literal table name, but a signifier that your code maps into a table name, which you then interpolate into the SQL query. This gives you more assurance that no SQL injection can occur.

HashMap h = new HashMap<String,String>();
/* user-friendly table name maps to actual, ugly table name */
h.put("accounts", "tbl_accounts123");

userTablename = ... /* user input */
if (h.containsKey(userTablename)) {
  tablename = h.get(userTablename);
} else {
  throw ... /* Exception that user input is invalid */
}
String sql = "SELECT MAX(AGE) FROM %s";
/* we know the table names are safe because we wrote them */
sql = String.format(sql, tablename); 

You definitely want to use PreparedStatements. They are convenient. Here is an example.