我有一个在底部实现smithWaterman算法的类，我已经决定将main放在GUI中并将其打印出矩阵。我一直得到NullPointerException。我不知道如何解决它，有没有人看到错误？谢谢。
package main;
import java.util.*;
import java.util.*;
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.List;
import java.lang.Math;
import javax.swing.DefaultListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.JTextPane;
import javax.swing.ListModel;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.TableColumn;
import javax.swing.table.TableModel;
import java.lang.Math;
/**
* Smith-Waterman Algorithm:
*
* @author Jomana Sherif Final Project SE 165 Fall2012
*/
public class smithWaterman2 {
// Initializing the two array lists of the input
StringBuffer store1 = new StringBuffer(0);
StringBuffer store2 = new StringBuffer(0);
String input1 = null;
String input2 = null;
double cell[][];
double matchValue = 1.0;
double misMatchValue = -0.3;
double diagonal = 0.0;
double gapValue = 0.3;
double max = 0.0;
int maxacross = 0;
int maxdown = 0;
/**
* Print Matrix
*
* @param args
*/
public void printMatrix() {
System.out.print(" | ");
for (int i = 0; i < input2.length(); i++) {
System.out.print(input2.charAt(i) + " | ");
}
System.out.println(" ");
for (int across = 0; across < input1.length(); across++) {
for (int down = 0; down < input2.length(); down++) {
if (down == 0) {
System.out.print(input1.charAt(across) + "|");
}
System.out.printf("%1$.1f", cell[across][down]);
System.out.print(" |");
}
System.out.println(" ");
}
}
public void generate() {
/**
* Creating the NxN matrix
*
* @param args
*/
cell = new double[input1.length()][input2.length()];
/**
* Computation
*
* @param args
*/
for (int across = 0; across < input1.length(); across++) {
for (int down = 0; down < input2.length(); down++) {
// Factor 1-3 goes here
/**
* Factor 1
*/
double match = 0.0;
double f2 = 0.0;
double f3 = 0.0;
if (input1.charAt(across) == (input2.charAt(down))) {
match = matchValue;
} else {
match = misMatchValue;
}
// diagonal
if (across < 1 || down < 1) {
diagonal = 0;
} else {
diagonal = cell[across - 1][down - 1];
}
double f1 = diagonal + match;
/**
* Factor 2
*/
for (int k = across - 1; k >= 0; k--) {
if (cell[k][down] != 0) {
f2 = cell[k][down] - (gapValue * (across - k));
}
}
/**
* Factor 3
*/
for (int l = down - 1; l >= 0; l--) {
if (cell[across][l] != 0) {
f3 = cell[across][l] - (gapValue * (down - l));
}
}
double cellValue = Math.max(Math.max(Math.max(f1, f2), f3), 0);
cell[across][down] = cellValue;
if (cellValue >= max) {
max = cellValue;
maxacross = across;
maxdown = down;
}
}
}
System.out.println("Max equals:" + max);
System.out.println("Max down:" + maxacross);
System.out.println("Max across:" + maxdown);
}
/**
* Optimal Solution Calculation
*/
public void optimal() {
int x = maxacross;
int y = maxdown;
// starting from the max
store1.append(input1.charAt(x));
store2.append(input2.charAt(y));
while (x > 0 && y > 0) {
double left = cell[x - 1][y];
double diagonal = cell[x - 1][y - 1];
double up = cell[x][y - 1];
if (left <= diagonal && up <= diagonal) {
x = x - 1;
y = y - 1;
store1.append(input1.charAt(x));
store2.append(input2.charAt(y));
} else if (left >= diagonal && left >= up) {
x = x - 1;
y = y;
store1.append(input1.charAt(x));
store2.append('-');
} else if (up >= diagonal && left <= up) {
x = x;
y = y - 1;
store1.append('-');
store2.append(input2.charAt(y));
}
}
store1.reverse();
store2.reverse();
System.out.println("store1:" + store1);
System.out.println("store2:" + store2);
}
/**
* Main Method
*/
public static void main(String[] args) {
smithWaterman2 sw = new smithWaterman2();
sw.generate();
sw.printMatrix();
sw.optimal();
}
}
答案 0 :(得分：6)
input2为空，但您在generate方法中的第一次调用是：
cell = new double[input1.length()][input2.length()];
当您尝试对空指针执行任何操作时，您正在调用input2.length();，结果为NullPointerExceptipon。
您的代码很容易出现NullPointerException。确保在调用任何操作时，引用不是null。