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像这种图形对称的由少变多再变少可以考虑绝对值控制。
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打个比方：就像在一个数轴上，越接近中心则距离越短，然后过了中心后，就会离中心越来越远。代码如下，如果n是可输入的，你用IO输入流代替即可。
public static void main(String[] args){
int n = 5;//*号的行数
/*控制*号的数量，最小为1，最大为n，由绝对值计算出变化*/
int m = 1;
int space = (n + 1) / 2;//空格的最大值
int s = 1;//和上面同理
for(int i = 0; i n; i++){
//控制空格输出
for(int j = 0; j Math.abs(space-s); j++){
System.out.print(" ");
}
s++;
//控制*号输出
for(int k = 0; k n - Math.abs(n - m); k++){
System.out.print("*");
}
m += 2;
System.out.println();
}
}
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
public class ReadBook extends JFrame {
JTextArea jta;
JTextField jtf;
JButton jb;
public ReadBook() {
jta = new JTextArea();
jtf = new JTextField(30);
jtf.setText("文件保存路径如c:\\ab.txt");
jb = new JButton("保存文字");
JPanel jp = new JPanel();
jp.add(jtf);
jp.add(jb);
add(jta);
add(jp, BorderLayout.SOUTH);
setBounds(500, 100, 500, 380);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
jb.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
//-------------核心代码---------
String path = jtf.getText();
File f = new File(path);
String txt = jta.getText().replaceAll("\n", "\r\n");
try {
BufferedWriter bw = new BufferedWriter(new FileWriter(f));
bw.write(txt);//写入文件中
bw.close();
} catch (Exception e1) {
e1.printStackTrace();
}
//-------------核心代码---------
}
});
}
public static void main(String[] args) {
new ReadBook();
}
}
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
public class vv extends JDialog {
private static final long serialVersionUID = 1L;
private JLabel l_Id = new JLabel("登陆账户", JLabel.CENTER);
private JLabel l_pw = new JLabel("登陆密码", JLabel.CENTER);
private JTextField t_Id = new JTextField(10);
private JPasswordField t_pw = new JPasswordField(10);
private JButton btnLogin;
private JButton btnClose;
public vv() {
super();
setResizable(false);
getContentPane().setBackground(new Color(225, 225, 225));
getContentPane().setLayout(null);
initialize();
}
protected void initialize() {
setTitle("系统登录");
l_Id.setBounds(48, 43, 53, 25);
t_Id.setBounds(110, 43, 150, 25);
l_pw.setBounds(48, 93, 53, 25);
t_pw.setBounds(110, 93, 150, 25);
getContentPane().add(l_Id);
getContentPane().add(l_pw);
getContentPane().add(t_Id);
getContentPane().add(t_pw);
btnLogin = new JButton();
btnLogin.setText("登 录");
btnLogin.setBounds(70, 142, 85, 28);
btnLogin.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
addBtnLoginActionListener();
}
});
getContentPane().add(btnLogin);
btnClose = new JButton();
btnClose.setText("关 闭");
btnClose.setBounds(175, 142, 85, 28);
btnClose.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
dispose();
System.exit(-1);
}
});
getContentPane().add(btnClose);
}
private void addBtnLoginActionListener() {
String user = t_Id.getText();
String password = new String(t_pw.getPassword());
if (user.equals("")) {
JOptionPane.showMessageDialog(this, "帐号不可为空", "Caution",
JOptionPane.WARNING_MESSAGE);
return;
}
if (password.equals("")) {
JOptionPane.showMessageDialog(this, "密码不可为空", "Caution",
JOptionPane.WARNING_MESSAGE);
return;
}
String sql = "select * FROM login WHERE id = '" + user + "' and pw = '"
+ password + "'";
boolean success = false;
// TODO:数据校验 success = executeQuery(sql);
if (success) {
// TODO： 如果数据校验成功 显示主界面 并关闭登录界面
JOptionPane.showMessageDialog(this, "成功登录", "提示",
JOptionPane.INFORMATION_MESSAGE);
this.dispose();
} else {
JOptionPane.showMessageDialog(this, "帐号或密码错误!", "警告",
JOptionPane.WARNING_MESSAGE);
t_pw.requestFocus(); // 密码框选中
}
}
public Dimension getPreferredSize() {
return new Dimension(320, 170);
}
public void show() {
Toolkit tk = Toolkit.getDefaultToolkit();
Dimension screen = tk.getScreenSize();
Dimension d = getSize();
this.setLocation((screen.width - d.width) / 2,
(screen.height - d.height) / 2);
// 输入密码后回车相当于点击了登录按钮
getRootPane().setDefaultButton(btnLogin);
t_pw.requestFocus();
setDefaultCloseOperation(DISPOSE_ON_CLOSE);
setSize(300, 220);
super.show();
}
public static void main(String[] args) {
vv loginFrame = new vv();
loginFrame.setVisible(true);
}
}
希望对你有帮助