英文:
Is there a way to print a multiline pattern on JOptionPane.showMessageDialog()?
问题
Sure, here's the translated code portion:
for (int row = 1; row <= L; row++) {
for (int col = 1; col <= L + L - 1; col++) {
if (row == L || row + col == L + 1 || col - row == L - 1)
System.out.print("*");
else
System.out.print(" ");
}
System.out.println();
}
Please note that the code you provided is in Java and seems to generate a pattern of a hollow pyramid using asterisks (*). If you have any further questions or need assistance with anything else, feel free to ask.
英文:
So I was wondering if there is a way to output a multiline pattern with stars (*) like a triangle or a pyramid on JOptionPane.showMessageDialog(). I know that this works like that: JOptionPane.showMessageDialog(null,"Hello World!"); but instead of Hello World! I need to print on the new window that pops up a hollow pyramid and I can't figure it out. Can you help me? Thanks in advance. I've added the code that prints the hollow pyramid. The variable L is the height of the pyramid and it is provided by the user whenever the program is executed. So how can I print this pattern with a variable height in a JOptionPane.showMessageDialog()?
for(int row=1;row<=L;row++){
for(int col=1;col<=L+L-1;col++){
if(row==L || row+col==L+1 || col-row==L-1) System.out.print("*");
else System.out.print(" ");
}
System.out.println();
}
答案1
得分: 2
不要有别的内容，只返回翻译好的部分：
而不是每次将文本逐个字符打印到 System.out，你应该将字符附加到一个字符串变量（最好使用 StringBuilder 以获得更好的性能）。
// 创建一个空字符串，并通过添加字符来生成金字塔
StringBuilder pyramid = new StringBuilder();
for (int row = 1; row <= L; row++) {
for (int col = 1; col <= L + L - 1; col++) {
if (row == L || row + col == L + 1 || col - row == L - 1)
pyramid.append("*");
else
pyramid.append(" ");
}
pyramid.append("\n");
}
// 输出与原始问题中所有微小的 System.out 写入相同的内容
System.out.println(pyramid);
对于一个较小的学术问题，没有完全必要进行优化；然而，为了以后的参考，当连接大量微小字符串时，应使用 StringBuilder。我提到这一点的原因是，内部实际上，当你“添加”（即连接）两个字符串时，每次都会分配一个新的字符串。当在循环中使用时，这可能会累积产生大量新的字符串分配。
注意，JOptionPane.showMessageDialog(...) 使用的默认字体不是等宽字体，默认情况下字符具有可变长度宽度。尝试有效地显示 ASCII 艺术可能效果不佳。可以通过使用一个不可编辑的透明文本区来解决这个问题：
JTextArea textbox = new JTextArea(pyramid);
textbox.setOpaque(false);
textbox.setEditable(false);
textbox.setFont(new Font("Monospaced", Font.BOLD, 12));
JOptionPane.showMessageDialog(null, textbox, "Pyramid", JOptionPane.PLAIN_MESSAGE);
这会产生以下效果：
英文:
Instead of printing text a few characters at a time to System.out, you should append the characters to a String variable (or ideally StringBuilder for better performance).
// create an empty string and generate the pyramid by adding characters
String pyramid = "";
for (int row = 1; row <= L; row++) {
for (int col = 1; col <= L + L - 1; col++) {
if (row == L || row + col == L + 1 || col - row == L - 1) pyramid += "*";
else pyramid += " ";
}
pyramid += "\n";
}
// outputs the same thing as all the tiny System.out writes in the original question
System.out.println(pyramid);
For a smaller academic problem, it is not totally necessary to optimize this; however, for future reference, you should use a StringBuilder when concatenating a significant amount of tiny strings. The reason I mention this is that internally, when you "add" (i.e. concatenate) two strings together, you are actually allocating another new string each time. This can add up to a lot of new allocations for strings when used in a loop.
<hr>
Note that the default font with JOptionPane.showMessageDialog(...) is not mono-spaced by default, meaning characters have variable length width. Trying to effectively display ASCII art might not work well. This can be circumvented by using a uneditable transparent text area:
JTextArea textbox = new JTextArea(pyramid);
textbox.setOpaque(false);
textbox.setEditable(false);
textbox.setFont(new Font("Monospaced", Font.BOLD, 12));
JOptionPane.showMessageDialog(null, textbox, "Pyramid", JOptionPane.PLAIN_MESSAGE);
This yields:<br>
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