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应该命名为boy.java。。。。
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类名是boy，不是boy extends Applet，extends只是描述。。。。
另外，类名建议首字母大写
求素数，比较经典的，下面是代码及注释
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public class Sushu {
/**
* 判断一个数是不是素数
* @param a 被判断的数
* @return 是素数返回真
*/
public boolean isSuhu(int a){
boolean isSushu=true;
//根据素数的性质判断一个数是否为素数
for(int i=2;ia;i++){
if(a%i==0){
isSushu=false;
break;
}
}
return isSushu;
}
/**
* 判断连续若干个数中那些是素数
* @param start 起始数
* @param end 终止数
*/
public void selectSushu(int start,int end){
//判断一串数中那些为素数，并将结果打印出来
for(int i=start;i=end;i++){
if(isSuhu(i)){
System.out.println(i);
}
}
}
public static void main(String []args){
//定义起始位置和终止位置
int start=1;
int end=100;
//声明变量
Sushu s=new Sushu();
//调用方法
s.selectSushu(start, end);
}
}
这是我晓得的最简单的java小程序代码了你可以看看:
package com.kenki.emp;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.sql.SQLException;
import java.sql.*;
public class emp extends HttpServlet {
private static final String CONTENT_TYPE = "text/html; charset=GBK";
//Initialize global variables
public void init() throws ServletException {
}
//Process the HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
response.setContentType(CONTENT_TYPE);
PrintWriter out = response.getWriter();
String code = request.getParameter("code");
String name = request.getParameter("name");
String pay = request.getParameter("pay");
System.out.println("empcode:" + code);
System.out.println("name:" + name);
System.out.println("pay:" + pay);
//创建驱动
new com.microsoft.jdbc.sqlserver.SQLServerDriver();
String strd =
"jdbc:microsoft:sqlserver://localhost:1433;databasename=emp_dates";
String username = "sa";
String pws = "";
try {
java.sql.Connection conn = java.sql.DriverManager.getConnection(
strd, username, pws);
String strs = "insert into emp values(?,?,?)";
java.sql.PreparedStatement pre = conn.prepareStatement(strs);
pre.setString(1, code);
pre.setString(2, name);
pre.setString(3, pay);
pre.execute();
pre.close();
conn.close();
//重定向至查询页面
out.println("成功保存！！");
response.sendRedirect("emp.html");
} catch (SQLException ss) {
ss.printStackTrace();
response.sendRedirect("/WebModule1/error.html");
}
}
//Process the HTTP Post request
public void doPost(HttpServletRequest request, HttpServletResponse response) throws
ServletException, IOException {
doGet(request, response);
}
//Clean up resources
public void destroy() {
}
}
import java.util.Scanner;
public class a {
public static void main(String[] args) {
String result=null;
double sum = 0;
int i=0;
String str = "";
do {
Scanner in = new Scanner(System.in);
System.out.print("输入姓名：");
String name=in.next();
System.out.print("输入学号：");
String num = in.next();
System.out.print("输入分数：");
double score = in.nextDouble();
i++;
sum+=score;
System.out.print("是否结束：(end/其它任意键)");
result = in.next();
str+=name+"\r"+num+"\r\t"+score+"\r";
} while (!result.equals("end"));
System.out.println("输出信息结果："+str+"\r\n");
System.out.println("平均分："+sum/i);
}
}
直接复制一下，就可以运行，看是不是你要的效果。（不过没有对输入的值做判断，自己可以对输入做一下判断）
这个也可以用for循环来做
我给你一个功能强大的计算器!已运行通过!
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Calculator3 extends JFrame implements ActionListener {
private boolean dotExist, operated, equaled; // 帮助运算的布尔变量
private double storedNumber; // 目前的结果
private char lastOperator; // 表示上一运算符
private JTextField operation; // 结果栏
private JButton dot, plus, minus, multi, div, sqrt, equal, changePN, clear; // 运算符
private JButton[] numbers; // 数字
// 构造者
public Calculator3() {
setTitle("Calculator");
// 初始化变量
dotExist = false; // 表示当前的数是否有小数点
operated = false; // 表示任意运算符是否被按下
equaled = false; // 表示等号是否被按下
storedNumber = 0;
lastOperator = '?';
// 初始化窗口变量
operation = new JTextField("0");
operation.setEditable(false);
numbers = new JButton[10];
for (int i = 0; i 10; i++)
numbers[i] = new JButton("" + i);
dot = new JButton(".");
plus = new JButton("+");
minus = new JButton("-");
multi = new JButton("*");
div = new JButton("/");
sqrt = new JButton("√");
equal = new JButton("=");
changePN = new JButton("±");
clear = new JButton("AC");
// 将窗口物体放入窗口
GridBagLayout layout = new GridBagLayout();
getContentPane().setLayout(layout);
addComponent(layout, operation, 0, 0, 4, 1);
addComponent(layout, numbers[1], 1, 0, 1, 1);
addComponent(layout, numbers[2], 1, 1, 1, 1);
addComponent(layout, numbers[3], 1, 2, 1, 1);
addComponent(layout, numbers[4], 2, 0, 1, 1);
addComponent(layout, numbers[5], 2, 1, 1, 1);
addComponent(layout, numbers[6], 2, 2, 1, 1);
addComponent(layout, numbers[7], 3, 0, 1, 1);
addComponent(layout, numbers[8], 3, 1, 1, 1);
addComponent(layout, numbers[9], 3, 2, 1, 1);
addComponent(layout, dot, 4, 0, 1, 1);
addComponent(layout, numbers[0], 4, 1, 1, 1);
addComponent(layout, sqrt, 4, 2, 1, 1);
addComponent(layout, plus, 1, 3, 1, 1);
addComponent(layout, minus, 2, 3, 1, 1);
addComponent(layout, multi, 3, 3, 1, 1);
addComponent(layout, div, 4, 3, 1, 1);
addComponent(layout, equal, 5, 0, 2, 1);
addComponent(layout, changePN, 5, 2, 1, 1);
addComponent(layout, clear, 5, 3, 1, 1);
}
// 对按钮进行反应的方法
public void actionPerformed(ActionEvent e) {
JButton btn = (JButton) e.getSource();
if (btn == clear) {
operation.setText("0");
dotExist = false;
storedNumber = 0;
lastOperator = '?';
} else if (btn == equal) {
operate('=');
equaled = true;
} else if (btn == plus) {
operate('+');
equaled = false;
} else if (btn == minus) {
operate('-');
equaled = false;
} else if (btn == multi) {
operate('*');
equaled = false;
} else if (btn == div) {
operate('/');
equaled = false;
} else if (btn == changePN) {
operate('p');
operate('=');
equaled = true;
} else if (btn == sqrt) {
operate('s');
operate('=');
equaled = true;
} else {
if (equaled)
storedNumber = 0;
for (int i = 0; i 10; i++)
if (btn == numbers[i]) {
if (operation.getText().equals("0"))
operation.setText("" + i);
else if (!operated)
operation.setText(operation.getText() + i);
else {
operation.setText("" + i);
operated = false;
}
}
if (btn == dot !dotExist) {
operation.setText(operation.getText() + ".");
dotExist = true;
}
}
}
// 进行运算的方法
private void operate(char operator) {
double currentNumber = Double.valueOf(operation.getText())
.doubleValue();
if (lastOperator == '?')
storedNumber = currentNumber;
else if (lastOperator == '+')
storedNumber += currentNumber;
else if (lastOperator == '-')
storedNumber -= currentNumber;
else if (lastOperator == '*')
storedNumber *= currentNumber;
else if (lastOperator == '/')
storedNumber /= currentNumber;
else if (lastOperator == 'p')
storedNumber *= -1;
else if (lastOperator == 's')
storedNumber = Math.sqrt(currentNumber);
else if (lastOperator == '=' equaled)
storedNumber = currentNumber;
operation.setText("" + storedNumber);
operated = true;
lastOperator = operator;
}
// 快捷使用GridBagLayout的方法
private void addComponent(GridBagLayout layout, Component component,
int row, int col, int width, int height) {
GridBagConstraints constraints = new GridBagConstraints();
constraints.fill = GridBagConstraints.BOTH;
constraints.insets = new Insets(10, 2, 10, 2);
constraints.weightx = 100;
constraints.weighty = 100;
constraints.gridx = col;
constraints.gridy = row;
constraints.gridwidth = width;
constraints.gridheight = height;
layout.setConstraints(component, constraints);
if (component instanceof JButton)
((JButton) component).addActionListener(this);
getContentPane().add(component);
}
// 主方法初始化并显示窗口
public static void main(String[] args) {
Calculator3 calc = new Calculator3();
calc.setSize(290, 400);
calc.setVisible(true);
}
}
代码如下：
public class HelloWorld {
public static void main(String []args) {
int a = 3, b = 7 ;
System.out.println("Hello World!");
}
public static int f(int a, int b){
return a*a + a*b + b*b;
}
}
结果如下：