Java 初始化 JComboBox[] 数组
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Initializing a JComboBox[] array
提问by PadlockCode
Sorry I am a noob at java, but how do i Initialize the variable petList without setting it equal to null?
抱歉，我是 Java 的菜鸟，但是如何在不将其设置为 null 的情况下初始化变量 petList？
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]);
}
采纳答案by Azad
Three things you must consider with creating arrays:
创建数组时必须考虑的三件事：
- Declaration:
JComboBox [] petList; - Initial the array:
petList = new JComboBox[someSize]; - Assigning:
petList[i] = new JComboBox();
- 宣言：
JComboBox [] petList; - 初始化数组：
petList = new JComboBox[someSize]; - 分配：
petList[i] = new JComboBox();
So, take the petListoutside the for-loop(maybe defining it as an instance variable will be better):
所以，把petList外面的for-loop（也许将它定义为一个实例变量会更好）：
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`
//........
}
}}
NOTE: this is not a compiled code, the will only demonstrates your solving your problem.
注意：这不是编译后的代码，它只会展示您解决问题的方法。
回答by nanofarad
You need to loop. This will incur other errors such as bounds overlapping, but this should be the gist:
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]);
}
