请教peek()与eof()的用法 请教peek注塑遇到的几个问题
\u8bf7\u6559java\u4e2dsetUI\u7684\u7528\u6cd5java\u4e2dsetUI\u7684\u7528\u6cd5\uff1a
\u8bed\u6cd5\uff1apublic void setUI(ComboBoxUI ui)
\u4e3e\u4f8b\uff1a
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.plaf.ComboBoxUI;
import javax.swing.plaf.ComponentUI;
import javax.swing.plaf.basic.BasicArrowButton;
import javax.swing.plaf.basic.BasicComboBoxUI;
public class Main {
public static void main(final String args[]) {
final String labels[] = { "A", "B", "C", "D", "E" };
JFrame frame = new JFrame("Popup JComboBox");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JComboBox comboBox = new JComboBox(labels);
comboBox.setUI((ComboBoxUI) MyComboBoxUI.createUI(comboBox));
frame.add(comboBox, BorderLayout.NORTH);
frame.setSize(300, 200);
frame.setVisible(true);
}
static class MyComboBoxUI extends BasicComboBoxUI {
public static ComponentUI createUI(JComponent c) {
return new MyComboBoxUI();
}
protected JButton createArrowButton() {
JButton button = new BasicArrowButton(BasicArrowButton.EAST);
return button;
}
}
}
\u6a21\u5177\u4e00\u822c\u7528140~180\u2103
\u901a\u5e38\uff0c\u6a21\u5177\u6e29\u5ea6\u7684\u5347\u9ad8\u4f1a\u51cf\u5c11\u5851\u6599\u5728\u578b\u8154\u6668\u6709\u51b7\u51dd\u5c42\uff0c\u4f7f\u7194\u878d\u6750\u6599\u5728\u578b\u8154\u5185\u66f4\u6613\u4e8e\u6d41\u52a8\uff0c\u4ece\u800c\u83b7\u5f97\u66f4\u5927\u7684\u96f6\u4ef6\u91cd\u91cf\u548c\u66f4\u597d\u7684\u8868\u9762\u8d28\u91cf\u3002\u540c\u65f6\uff0c\u6a21\u5177\u6e29\u5ea6\u7684\u63d0\u9ad8\u8fd8\u4f1a\u4f7f\u96f6\u4ef6\u5f20\u529b\u5f3a\u5ea6\u589e\u52a0\u3002
\u52a0\u5165\u6ed1\u77f3\u7c89\u53ea\u4f1a\u4f7f\u8868\u9762\u5149\u6cfd\u66f4\u5dee\u2026\u2026\u6210\u54c1\u5f3a\u5ea6\u66f4\u5dee\u2026\u2026
读回的不是EOF，则存在读缓冲器里
rdbuf()->sgetc()
while( fin.peek()!=EOF ) {
如果temp.txt有4行，第4行有新行符号没别的东西，
则循环4次，遇到 EOF 退出
第4次 读缓冲器里的内容是第三次读入的
所以 多一个 cc
eof 是文件结束符号， 编码是 ffff
temp.txt
aa
bb
ccEOF
--------------
与
aa
bb
cc
EOF
----------
前者3行，后者4行
改为：
while( fin.peek()!=EOF ) {
ch[0] = '\0';
fin >> ch;
cout << ch;
}
就好了。
peek调用形式为cin.peek() 其返回值是一个char型的字符，其返回值是指针指向的当前字符，但它只是观测，指针仍停留在当前位置，并不后移。如果要访问的字符是文件结束符，则函数值是EOF（-1）
例如
#include <iostream>
using namespace std;
int main () {
char c;
int n;
char str[256];
cout << "Enter a number or a word: ";
c=cin.peek();
if ( (c >= '0') && (c <= '9') )
{
cin >> n;
cout << "You have entered number " << n << endl;
}
else
{
cin >> str;
cout << " You have entered word " << str << endl;
}
return 0;
}
（以上参考资料为百度百科peek函数）
易于理解其用法
C语言中，EOF常被作为文件结束的标志。还有很多文件处理函数处错误后的返回值也是EOF，因此常被用来判断调用一个函数是否成功。
例如：
#include <stdio.h>
int main(void)
{
int n,i;
int array[25];
while (scanf("%d",&n),n!=EOF) //while(scanf("%d",&n)!=EOF)
{
for (i=0; i<n; i++)
scanf("%d",array+i);
for (i=0; i<n; i++)
printf ("%d ",array[i]);
}
return 0;
}
（以上参考资料为百度百科eof）
不懂情追问。
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