java bubblesort with acm dialog
- by qzar
Hi,
the program gives following exception:
Exception in thread "main" java.lang.NullPointerException
at myclasses.BubbleSort.run(BubbleSort.java:42)
at acm.program.Program.runHook(Program.java:1519)
at acm.program.Program.startRun(Program.java:1508)
at acm.program.Program.start(Program.java:729)
at myclasses.BubbleSort.main(BubbleSort.java:49)
what is wrong?
thank you very much!
package myclasses;
import acm.program.DialogProgram;
public class BubbleSort extends DialogProgram {
int[] array;
public int[] getArray() {
return array;
}
public void setArray(int[] array) {
this.array = array;
}
void swap(int firstPos, int secondPos) {
int temp = array[firstPos];
array[firstPos] = array[secondPos];
array[secondPos] = temp;
}
public void bubblesort() {
int i, j, k;
for (i = 1; i < array.length; i++) {
j = i;
k = array[i];
while (j > 0 && array[j - 1] > k) {
array[j] = array[j - 1];
--j;
}
array[j] = k;
}
}
public void run() {
BubbleSort a = new BubbleSort();
a.setArray(new int[] {1, 3, 5, 7, 6, 2});
a.bubblesort();
StringBuffer sb = new StringBuffer(a.array.length * 2);
for (int i = 0; i < getArray().length; i++) sb.append(getArray()[i]).append(" ");
println(sb);
}
public static void main(String[] args) {
new BubbleSort().start(args);
}
}
