无法使用Java中的参数化构造函数实例化对象

Question

This is the class I want to Instantiate:

public class GoogleSheetsAPI {

String spreadsheetId;
Sheets service;
String credentialsFile;

public void GoogleSheetsAPI() {
}

public void GoogleSheetsAPI(String spreadsheetId, String credentialsFile) throws Exception {
    this.spreadsheetId = spreadsheetId;
    this.credentialsFile = credentialsFile;
    service = getSheetsService();
}

}

This is how I am creating an object of class GoogleSheetsAPI

GoogleSheetsAPI googleSheetsAPI = new GoogleSheetsAPI(spreadsheetId, credentiialsFile);

Answer 1

The constructor must not have void , it should be:

public GoogleSheetsAPI(String spreadsheetId, String credentialsFile) throws Exception {
    this.spreadsheetId = spreadsheetId;
    this.credentialsFile = credentialsFile;
    service = getSheetsService();
}

Answer 2

构造函数没有任何返回类型...因为这是一种特殊方法，如果您定义自己的构造函数，则不要定义空构造函数，因为jvm提供了默认值...

Answer 3

Class.newInstance invokes the no-arg constructor

Class<?> cl = Class.forName("javax.swing.JLabel");
Constructor<?> cons = cl.getConstructor(String.class);

Object o = cons.newInstance("JLabel");

to invoke a different constructor, you need to use the reflection package (java.lang.reflect).