java - 返回查询 SELECT 语句

Question

我试图从作者表中返回所有ID...但不起作用...只是返回第一个ID...但是如果我删除返回并放入打印，那么就会给我所有ID..

String url = "jdbc:postgresql://localhost/testdb";
String user = "test";
String password = "test*";

try {
    con = DriverManager.getConnection(url, user, password);
    pst = con.prepareStatement("SELECT id FROM authors");
    rs = pst.executeQuery();

    while (rs.next()) {
        return rs.getInt(1);
    }

Answer 1

return 语句默认返回返回的常量/变量的值，停止方法执行并离开该方法。对此进行了解释:Returning a Value from a Method

要返回查询执行的所有结果，您必须将结果存储在 List 中，然后返回此列表:

List<Integer> idList = new ArrayList<Integer>();
//accessing to the database and executing the query...
rs = pst.executeQuery();
while (rs.next()) {
    //store the ids in the list
    idList.add(rs.getInt(1));
}
//close all the resources...
//at the bottom of your method
return idList;