Select * in SOQL using Apex Class

gistfile1.cls

String table = 'TableName'; // with __c if use Custom Object
Map<String, Schema.SObjectType> m = Schema.getGlobalDescribe() ;
Schema.SObjectType s = m.get(table) ;
Schema.DescribeSObjectResult r = s.getDescribe() ;
Map<String, Schema.SObjectField> fields = r.fields.getMap() ;
string soql = '';
for (String fieldName : fields.keyset()) {
	if (soql != '') {
		soql += ', ';
	}
	soql += fieldName;
}
soql = 'SELECT ' + soql + ' FROM ' + table;
System.debug(soql);
List<TableName> acs = Database.query(soql);
System.debug(acs.get(0));

withMethod.cls

/**
     * Bring Select * into SOQL
     * @param tableName tableName
     * @param whereCondition cover WHERE, GROUP BY, ORDER BY, AND LIMIT
     * @param isCustomFieldOnly set true if only to get custom fields
     * @return String string concat query
     **/
    public static String getSelectAllQuery(String tableName, String whereCondition, Boolean isCustomFieldOnly) {
        Map<String, Schema.SObjectType> m = Schema.getGlobalDescribe() ;
        Schema.SObjectType s = m.get(tableName) ;
        Schema.DescribeSObjectResult r = s.getDescribe() ;
        Map<String, Schema.SObjectField> fields = r.fields.getMap() ;
        string soql = '';
        for (String fieldName : fields.keyset()) {
            if (soql != '') {
                soql += ', ';
            }
            if(isCustomFieldOnly && (fieldName.indexOf('__c') < 0)) {
                continue;
            }
            soql += fieldName;
        }
        soql = 'SELECT ' + soql + ' FROM ' + tableName + ' ' + whereCondition;
        return soql;
    }