我的代码适用于扩展二项式的applet。我还没有完成它，但它只接受1到10之间的指数，包括1和10。我得到了7，但就像我说的那样，我还没完成。我的问题是这样的：在第一个textField中，它将接受一个数字和一个变量（如4a或其他东西）。我写的代码不能考虑这个数字（它应该只接受一个变量）。所以...我如何得到它，以便第一个textField不允许有一个int？谢谢！
import java.applet.Applet;
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.*;
import java.text.DecimalFormat;
import java.util.ArrayList;
import javax.swing.Action;
public class BinomialExpander extends JApplet implements ActionListener
{
JLabel welcome;
JLabel directions;
JLabel example;
JLabel instructions;
JLabel startOfBinomial;
JLabel plusSign;
JLabel forExponent;
JLabel endOfBinomial;
JTextField firstVar;
JTextField txtSecond;
JTextField exp;
JLabel lblExpanded;
JLabel outputExpanded;
FlowLayout layout;
JButton compute;
private int[] pascal1 = {1,1};
private int[] pascal2 = {1,2,1};
private int[] pascal3 = {1,3,3,1};
private int[] pascal4 = {1,4,6,4,1};
private int[] pascal5 = {1,5,10,10,5,1};
private int[] pascal6 = {1,6,15,20,15,6,1};
private int[] pascal7 = {1,7,21,35,35,21,7,1};
private int[] pascal8 = {1,8,28,56,70,56,28,8,1};
private int[] pascal9 = {1,9,36,84,126,84,36,9,1};
private int[] pascal10 = {1,10,45,120,210,120,45,10,1};
private String a;
private int y;
private int expo;
private String x;
public void init()
{
Container c = getContentPane();
c.setBackground(Color.pink);
layout = new FlowLayout();
layout.setAlignment(FlowLayout.LEFT);
c.setLayout(layout);
setSize(500,175);
welcome = new JLabel("Welcome to the Binomial Expander Applet!");
welcome.setFont(new Font("Copperplate Gothic Bold", Font.PLAIN, 16));
directions = new JLabel("Enter binomial ONLY in the form: (VARIABLE + NUMBER)^EXPONENT");
directions.setFont(new Font("Times New Roman", Font.PLAIN, 14));
example = new JLabel("EXAMPLE: (x + 2)^2.");
instructions = new JLabel("Enter the variable of your binomial:");
startOfBinomial = new JLabel(" (");
firstVar = new JTextField(4);
plusSign = new JLabel(" + ");
txtSecond = new JTextField(4);
endOfBinomial = new JLabel(")");
forExponent = new JLabel("^");
forExponent.setFont(new Font("Times New Roman", Font.PLAIN, 10));
exp = new JTextField(2);
compute = new JButton("Compute!");
compute.addActionListener(this);
lblExpanded = new JLabel("Your expanded binomial is: ");
outputExpanded = new JLabel("");
c.add(welcome);
c.add(directions);
c.add(example);
c.add(instructions);
c.add(startOfBinomial);
c.add(firstVar);
c.add(plusSign);
c.add(txtSecond);
c.add(endOfBinomial);
c.add(forExponent);
c.add(exp);
c.add(compute);
c.add(lblExpanded);
c.add(outputExpanded);
}
public void actionPerformed(ActionEvent event)
{
a = firstVar.getText();
y = Integer.parseInt(txtSecond.getText());
expo = Integer.parseInt(exp.getText());
outputExpanded.setText(expand());
}
public String expand()
{
if (expo < 1 || expo > 10)
{
x = "ERROR: Exponent value must be between 1 and 10, inclusive.";
return x;
}
else if (expo == 1)
{
x = a + "+" + y;
return x;
}
else if (expo == 2)
{
x = a + "^" + expo + " + " + (pascal2[1] * y) + a + " + " + (pascal2[2] * Math.pow(y, expo));
return x;
}
else if (expo == 3)
{
x = a + "^" + expo + " + " + (pascal3[1] * y) + a + "^" + (expo-1) + (pascal3[2] * Math.pow(y, expo-1)) + a + " + " + (Math.pow(y, expo));
return x;
}
else if (expo == 4)
{
x = a + "^" + expo + " + " + (pascal4[1] * y) + a + "^" + (expo-1) + " + " + (pascal4[2] * Math.pow(y, expo-2)) + a + " ^ " + (expo-2) + " + " + (pascal4[3] *
Math.pow(y, expo-1)) + a + "+" + (Math.pow(y,expo));
return x;
}
else if (expo == 5)
{
x = a + "^" + expo + " + " + (pascal5[1] * y) + a + "^" + (expo-1) + " + " + (pascal5[2] * Math.pow(y,expo-3)) + a + "^" + (expo-2) + " + " + (pascal5[3] *
Math.pow(y, expo-2)) + a + "^" + (expo-3) + " + " + (pascal5[4] * Math.pow(y, expo-1)) + a + " + " + (Math.pow(y, expo));
return x;
}
else if (expo == 6)
{
x = a + "^" + expo + " + " + (pascal6[1] * y) + a + "^" + (expo-1) + " + " + (pascal6[2] * Math.pow(y, expo-4)) + a + "^" + (expo-2) + " + " + (pascal6[3] *
Math.pow(y, expo-3)) + a + "^" + (expo-3) + " + " + (pascal6[4] * Math.pow(y, expo-2)) + a + "^" + (expo-4) + " + " + (pascal6[5] * Math.pow(y, expo-1)) +
a + " + " + (Math.pow(y,expo));
return x;
}
else if (expo == 7)
{
x = a + "^" + expo + " + " + (pascal7[1] * y) + a + "^" + (expo-1) + " + " + (pascal7[2] * Math.pow(y, expo-5)) + a + "^" + (expo-2) + " + " + (pascal7[3]
* Math.pow(y, expo-4)) + a + "^" + (expo-3) + " + " + (pascal7[4] * Math.pow(y, expo-3)) + a + "^" + (expo-4) + " + " + (pascal7[5] * Math.pow(y, expo-2))
+ a + "^" + (expo-5) + (pascal7[6] * Math.pow(y, expo-1)) + a + " + " + (Math.pow(y, expo));
return x;
}
return x;
}
}
答案 0 :(得分：0)
假设a是您想要删除数字的字符串，请尝试使用
a = a.replaceAll("[0-9]*$", "");
将取出所有数字。
答案 1 :(得分：0)
我建议使用String's match()函数来查看a中的值是否为有效答案（我不知道什么对您有效）。然后，如果它无效，您可以使用JDialog来显示错误消息，而不是计算二项式。
它看起来像这样：
public void actionPerformed(ActionEvent event)
{
a = firstVar.getText();
y = Integer.parseInt(txtSecond.getText());
expo = Integer.parseInt(exp.getText());
if(a.matches(/*Some REGEX*/)) {
outputExpanded.setText(expand());
}
else {
//Use the JDialog
}
}
以下是页面：
答案 2 :(得分：0)
上述答案足以满足您的提问。让我有点多管闲事，并指出通过使用循环而不是硬编码指令可以大大改进（和缩短）代码。
我快速准备了以下代码：
public static float coefficient（int n，int k）{ int sup = 1; int inf = 1; for（int i =（n-k）+1; i＆lt; = n; i ++）{ sup * = i; } for（int i = 2; i＆lt; = k; i ++）{ inf * = i; } 返回（sup / inf）; }
public static String Binomials(int limit, int y, String variable) {
StringBuilder result = new StringBuilder("");
for (int i = 0; i <= limit; i++) {
if (i>0) {
result.append("+"+variable );
if (i>1) {
result.append("^" + i );
}
result.append("*");
}
result.append( Math.pow(y, limit-i) * coefficient(limit, i));
}
return (result.toString());
}
它没有经过彻底的测试，也没有提高效率，但似乎工作得很好。因此，我相信它可以作为您创建方法的通用版本的基础。