Java - escape string to prevent SQL injection

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.

The only way to prevent SQL injection is with parameterized SQL. It simply isn't possible to build a filter that's smarter than the people who hack SQL for a living.

So use parameters for all input, updates, and where clauses. Dynamic SQL is simply an open door for hackers, and that includes dynamic SQL in stored procedures. Parameterize, parameterize, parameterize.