我正在制作一个简单的代码生成器(非随机),但我遇到了一个问题。用户将数据输入7个文本域;然后将其内容放入String类型的数组中。然后我的代码接受该数组,分析不同的元素并吐出一个可用的代码(由我)。
但是,在我尝试标准化String数组(也就是将每个元素设置为小写字符串)时,它会导致整个程序停止工作,并且我得到的似乎是空指针异常。
我的具体错误信息如下:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at inventorycodeconverter.codeDisplay.calculateData(codeDisplay.java:48)
at inventorycodeconverter.InventoryCodeConverterView.button1ActionPerformed(InventoryCodeConverterView.java:315)
at inventorycodeconverter.InventoryCodeConverterView.access$900(InventoryCodeConverterView.java:23)
at inventorycodeconverter.InventoryCodeConverterView$5.actionPerformed(InventoryCodeConverterView.java:211)
at java.awt.Button.processActionEvent(Button.java:392)
at java.awt.Button.processEvent(Button.java:360)
at java.awt.Component.dispatchEventImpl(Component.java:4630)
at java.awt.Component.dispatchEvent(Component.java:4460)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
似乎给出麻烦的代码部分是这样的:
public void calculateData(){
int i;
for (i = 0; i < calculationBuffer.length; i++){ // calculationBuffer is defined and initialized elsewhere.
calculationBuffer[i] = calculationBuffer[i].toLowerCase();// this is line 48 where the first error appears to be.
}
if (calculationBuffer[0].equals("cap")){
displayBuffer[0] = "CAP"; // displayBuffer is defined and initialized elsewhere.
}
else {
displayBuffer[0] = "#Error#";
}
if (calculationBuffer[1].equals("20/400")) {
theTA.append("B");
}
else if (calculationBuffer[1].equals("20/410")){
displayBuffer[1] = "C";
}
else if (calculationBuffer[1].equals("24/410")){
displayBuffer[1] = "F";
}
else if (calculationBuffer[1].equals("24/415")) {
displayBuffer[1] = "Y";
}
else if (calculationBuffer[1].equals("28/400")){
displayBuffer[1] = "H";
}
else if (calculationBuffer[1].equals("28/415")) {
displayBuffer[1] = "X";
}
else if (calculationBuffer[1].equals("28/410")) {
displayBuffer[1] = "I";
}
else if (calculationBuffer[1].equals("33/400")) {
displayBuffer[1] = "J";
}
else if (calculationBuffer[1].equals("38/400")) {
displayBuffer[1] = "K";
}
else if (calculationBuffer[1].equals("43/400")) {
displayBuffer[1] = "M";
}
else if (calculationBuffer[1].equals("45/400")) {
displayBuffer[1] = "N";
}
else if (calculationBuffer[1].equals("58/400")) {
displayBuffer[1] = "Q";
}
else if (calculationBuffer[1].equals("70/400")) {
displayBuffer[1] = "S";
}
else if (calculationBuffer[1].equals("89/400")) {
displayBuffer[1] = "T";
}
}
public void displayData() {
String displayString;
displayString = Arrays.toString(displayBuffer);
StringTokenizer st = new StringTokenizer(displayString, ",");
while(st.hasMoreTokens()){
String finalText = st.nextToken();
theTA.append(finalText);
}
}
答案 0 :(得分:4)
某处您已将数组声明为以下(可能):
String[] calculationBuffer = new String[size];
它会使用null
初始化所有索引。因此你得到了NPE。
在使用数组
之前,您应该如下所示填充循环中的所有索引for(int i=0; i<size; i++)
{
calculationBuffer[i] = "A String";
}
答案 1 :(得分:2)
如果要声明像String[] calculationBuffer = new String[size];
然后所有的字符串元素都被Null初始化,所以如果你没有在其他地方的字符串数组中添加值,那么你可以像这样更新你的代码
for (i = 0; i < calculationBuffer.length; i++){
**calculationBuffer[i]="";**
calculationBuffer[i] = calculationBuffer[i].toLowerCase();// this is line 48 where the first error appears to be.
}
由于
答案 2 :(得分:0)
你在哪里填写你的计算缓冲区?
你得到的错误表明calculateBuffer [i]为null意味着你没有正确填充你的初始数组。