好的,我需要一个重新创建帕斯卡三角形的类。我们正在使用 BlueJ,我无法让我的数组相互访问。这是代码:
public class PascalTriangle {
private int currentLineNumber;
private int[] previousLineArray;
private int[] nextLineArray;
public void firstLine()
{
currentLineNumber = 1;
System.out.println("1");
}
public void nextLine()
{
if (currentLineNumber == 1) {
int [] previousLineArray = new int [(currentLineNumber+1)];
previousLineArray[0] = 1;
previousLineArray[1] = 1;
System.out.println("1 1");
currentLineNumber = 2;
}
else if(currentLineNumber >= 2) {
for (int lineCount = currentLineNumber; lineCount <= currentLineNumber; lineCount++) {
int [] nextLineArray = new int [(lineCount+1)];
nextLineArray[0] = 1;
System.out.print(nextLineArray[0] + " ");
for (int nextLineCount = 1; nextLineCount < lineCount; nextLineCount++) {
// The next line is the line with the NullPointerException
nextLineArray[(nextLineCount)] = (previousLineArray[(nextLineCount-1)
+ previousLineArray[(nextLineCount)]]);
System.out.print(nextLineArray[(nextLineCount)] + " ");
}
nextLineArray[(lineCount)] = 1;
System.out.print(nextLineArray[(lineCount)] + "\n");
previousLineArray = nextLineArray;
}
currentLineNumber = currentLineNumber+1;
}
}
}
该类将编译,但当我到达第三行时,应该读为1 2 1
,我java.lang.NullPointerException
在PascalTriangle.nextLine(PascalTriangle.java:29)
它处得到了一个突出显示该行的nextLineArray[(nextLineCount)] = (previousLineArray[(nextLineCount-1)
行。为什么 nextLineArray 会从nextLine()
第一次调用该方法时设置的 previousLineArray 中获取信息?
任何帮助将不胜感激:) 谢谢。