Question

抱歉，我是java的菜鸟，但是如何初始化变量petList而不将其设置为null？

for (int x = 0;x<= buttonPressed;x++){

    println("adding box");
    String[] petStrings = { "Withdraw", "Deposit", "Blah", };

    //Create the combo box, select item at index 4.
    @SuppressWarnings({ "rawtypes", "unchecked" })
    JComboBox petList[] = null;// = new JComboBox(petStrings);
    petList[x] = new JComboBox(petStrings);
    petList[x].setSelectedIndex(1);
    petList[x].setBounds(119, (buttonPressed *20)+15, 261, 23);

    contentPane.add(petList[x]);        
}

Answer 1

创建数组时必须考虑三件事：

声明：JComboBox [] petList;
初始化数组：petList = new JComboBox[someSize];
分配：petList[i] = new JComboBox();

所以，在petList之外取for-loop（可能将其定义为实例变量会更好）：

public class YourClass{
//instance variables 
private JComboBox[] petList; // you just declared an array of petList
private static final int PET_SIZE = 4;// assuming
//Constructor
public YourClass(){
 petList = new JComboBox[PET_SIZE];  // here you initialed it
 for(int i = 0 ; i < petList.length; i++){
  //.......
  petList[i] = new JComboBox(); // here you assigned each index to avoid `NullPointerException`
 //........
 }
}}

注意：这不是编译代码，只会证明您解决问题。

Answer 2

你需要循环。这将导致其他错误，例如边界重叠，但这应该是要点：

JComboBox[] petList = new JComboBox[petStrings.length];
for(int i=0; i<petStrings.length; i++){
    petList[i]=new JComboBox(petStrings[i]);
}

初始化JComboBox []数组

2 个答案: