Thanks for helping me out. I've been going through your examples lately. I found out that some of the examples don't compile any more and some use deprecated methods. I supply at the end codes for some of them that actually compile. If you like, please use them to replace the outdated examples. It could be easier for a new guy like me.

Extract table names from SQL
statement = CCJSqlParserUtil.parse("SELECT * FROM MY_TABLE1 JOIN MY_TABLE1");
TablesNamesFinder tablesNamesFinder = new TablesNamesFinder();
Set tables = tablesNamesFinder.getTables(statement);
Apply aliases to all expressions
select = (Select) CCJSqlParserUtil.parse("select a,b,c from test");
final AddAliasesVisitor instance = new AddAliasesVisitor();
select.getPlainSelect().accept(instance, null);

Extending a simple insert
insert = (Insert)CCJSqlParserUtil.parse("insert into mytable (col1) values (1)");
System.out.println(insert.toString());

insert.getColumns().add(new Column("col2"));

ExpressionVisitorAdapter expressionVisitorAdapter = new ExpressionVisitorAdapter<>() {

@Override
public <S> LongValue visit(ExpressionList<? extends Expression> expressionList, S context) {
 
 LongValue r = visitHelper(expressionList);
 return r;
 
}
private LongValue visitHelper(ExpressionList expressionList) {
 
 LongValue l = new LongValue(5);
 expressionList.addExpression(l);
 return l;
}

};

 ((ExpressionList)insert.getValues().getExpressions()).accept(expressionVisitorAdapter, null);

System.out.println(insert.toString());

insert.getColumns().add(new Column("col3"));

((ExpressionList)insert.getValues().getExpressions()).addExpression(new LongValue(10));

System.out.println(insert.toString());

Replacing String values
String sql ="SELECT NAME, ADDRESS, COL1 FROM USER WHERE SSN IN ('11111111111111', '22222222222222');";
select = (Select) CCJSqlParserUtil.parse(sql);

StringBuilder buffer = new StringBuilder();
ExpressionDeParser expressionDeParser = new ExpressionDeParser() {

 @Override
 public <S> StringBuilder visit(StringValue stringValue, S context) {
 this.getBuffer().append("XXXX");
 return null;
 }

};

SelectDeParser deparser = new SelectDeParser(expressionDeParser, buffer);
expressionDeParser.setSelectVisitor(deparser);
expressionDeParser.setBuffer(buffer);
select.getPlainSelect().accept(deparser, null);

System.out.println(buffer.toString());

More general replacing of String values in Statements
public class ReplaceColumnValues {

static class ReplaceColumnAndLongValues extends ExpressionDeParser {
 @Override
 public <S> StringBuilder visit(StringValue stringValue, S context) {
 this.getBuffer().append("?");
 return null;
 }
 
 @Override
 public <S> StringBuilder visit(LongValue longValue, S context) {
 this.getBuffer().append("*");
 return null;
 }
 
}
public static String cleanStatement(String sql) throws JSQLParserException {
 StringBuilder buffer = new StringBuilder();
 ExpressionDeParser expr = new ReplaceColumnAndLongValues();
 SelectDeParser selectDeparser = new SelectDeParser(expr, buffer);
 expr.setSelectVisitor(selectDeparser);
 expr.setBuffer(buffer);
 StatementDeParser stmtDeparser = new StatementDeParser(expr, selectDeparser, buffer);
 Statement stmt = CCJSqlParserUtil.parse(sql);
 stmt.accept(stmtDeparser);
 return stmtDeparser.getBuffer().toString();
}
public static void main(String[] args) throws JSQLParserException {
 System.out.println(cleanStatement("SELECT 'abc', 5 FROM mytable WHERE col='test'"));
 System.out.println(cleanStatement("UPDATE table1 A SET A.columna = 'XXX' WHERE A.cod_table = 'YYY'"));
 System.out.println(cleanStatement("INSERT INTO example (num, name, address, tel) VALUES (1, 'name', 'test ', '1234-1234')"));
 System.out.println(cleanStatement("DELETE FROM table1 where col=5 and col2=4"));
}

}

Retrieve all selected items of a SQL statement
stmt = (Select) CCJSqlParserUtil.parse("SELECT col1 AS a, col2 AS b, col3 AS c FROM table WHERE col_1 = 10 AND col_2 = 20 AND col_3 = 30");
System.out.println("before " + stmt.toString());

stmt.getPlainSelect().getWhere().accept(new ExpressionVisitorAdapter<>() {

 @Override
 public <S> Column visit(Column column, S context) {
 column.setColumnName(column.getColumnName().replace("_", ""));
 return null;
 }

}, null);

System.out.println("after " + stmt.toString());