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java求e代码 java代码示例
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用JAVA的成员方法求：e=1+1/1!=1/2!+1/3!+.....+1/n!
public class test1 { float getfloat(int n) { int s=0; if(n=0) return 1; for(int i=1;i=n;i++) s=s+i; return 1/s; } public static void main(String[] args)throws Exception { int n=System.in.read(); float e=0; for(int i=0;i=n;i++) { e=e+getfloat(i); } } }
相关问答
Q1: java中怎么用自然对数的底e
调用Java Math.log()方法使用e。
1.描述：
java.lang.Math.log(double a) 返回自然对数（以e为底）的一个double值。特殊情况：
如果参数是NaN或小于零，那么结果是NaN.
如果参数是正无穷大，那么结果是正无穷大。
如果参数是正零或负零，那么结果是负无穷大。
2.以下是java.lang.Math.log()方法的声明：
public static double log(double a)
Q2: Java中用数组输出E到H，这是小菜鸟编写的代码，请指教错误之处。谢谢！再次谢谢！
你的程序明显错了,主要是在循环的地方错了
do
{
a[i]=(char)('E'+i); //a[0]='E'
System.out.println(a[i]); //输出a[0],即输出'E'
i++; //i++,执行完之后i=1
}
while(a[i]=='H'); //a[1]现在为空,不可能等于'H',而且之后的a[2],a[3]....在这里也是这样!
这样改改吧
int i = -1;
do
{
i++;
a[i]=(char)('E'+i);
System.out.println(a[i]);
}
while(a[i]=='H');
Q3: Java编程题！新人，求代码，最好有详细的注解！感谢各位大神~
环境：JDK1.8+。然后复制粘贴代码即可用。
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.stream.Collectors;
public class MainController {
public static void main(String[] args) {
//一.将图一四个人的信息放入list中
ListStudent students = new ArrayList();
Student s1 = new Student("小赵",getTime("1992.08.11"),400);
Student s2 = new Student("小钱",getTime("1995.01.24"),750);
Student s3 = new Student("小孙",getTime("1990.06.05"),670);
Student s4 = new Student("小李",getTime("1991.12.17"),550);
students.add( s1 );
students.add( s2 );
students.add( s3 );
students.add( s4 );
//二.计算四个人成绩的平均值java求e代码，并输出每个人比平均值多或少多少分。
System.out.println("二.计算四个人成绩的平均值，并输出每个人比平均值多或少多少分。");
average( students );
//三.将四人排序输出，控制台输出结果请参照图二
System.out.println("三.将四人排序输出，控制台输出结果请参照图二");
sort( students );
//四.用递归计算出小赵的成绩以每月2%的增长，多少个月后他的成绩可以超过小钱。
System.out.println("四.用递归计算出小赵的成绩以每月2%的增长，多少个月后他的成绩可以超过小钱。");
markBeyong( students.get(0).getMark() , students.get(1).getMark() );
}
public static void average( ListStudent students ){
int sum = 0;//总成绩
for ( Student student: students ){
sum = sum + student.getMark();
}
int average = sum/students.size();//平均成绩
students.forEach( student - {
if ( student.getMark() average ){
System.out.println( student.getName() + "比平均分高:" + (student.getMark() - average) );
}else if ( student.getMark() average ){
System.out.println( student.getName() + "比平均分低:" + ( average - student.getMark()) );
}else {
System.out.println( student.getName() + "和平均分一样" );
}
} );
}
public static void sort( ListStudent students ){
ListStudent studentBir = new ArrayList();
studentBir.addAll( students );
System.out.println("①第一种排序，按照出生年月日升序java求e代码；");
Collections.sort( studentBir, (o1, o2) - ( o1.getBirthDay().compareTo( o2.getBirthDay() ) ) );
studentBir.forEach( stu -{
System.out.println( stu.getName() + " | " + getTime(stu.getBirthDay()) + " | " + stu.getMark() );
} );
System.out.println(" ②第二种排序，按照成绩降序；");
ListStudent markDesc = students.stream().sorted((a, b) - b.getMark() - a.getMark()).collect(Collectors.toList());
markDesc.forEach( stu -{
System.out.println( stu.getName() + " | " + getTime(stu.getBirthDay()) + " | " + stu.getMark() );
} );
System.out.println("③比较输出:计算他们互相大多少天，要考虑到闰年。");
for ( int i = 0 ; i students.size() ; i++ ){
for ( int j = i + 1 ; j students.size() ; j++ ){
Long ageSub = students.get( i ).getBirthDay().getTime() - students.get( j ).getBirthDay().getTime();
Long dateSub = ageSub/(1000*60*60*24);
if ( dateSub 0 ){
System.out.println( students.get( i ).getName() + "比" + students.get( j ).getName() + "大" + dateSub );
}else if ( dateSub 0 ){
System.out.println( students.get( i ).getName() + "比" + students.get( j ).getName() + "小" + -dateSub );
}else {
System.out.println( students.get( i ).getName() + "和" + students.get( j ).getName() + "同日出生" );
}
}
}
}
public static void markBeyong( int mark ,int targetMark){
double markDou = mark;
double targetMarkDou = targetMark;
boolean b = true;
int month = 0;
while ( b ){
if ( markDou targetMarkDou ){
markDou = markDou*1.02;
month ++;
}else {
System.out.println("一共用了" + month + "个月反超");
b = false;
}
}
}
public static Date getTime( String target ) {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM.dd");
Date date = sdf.parse(target);
return date;
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
public static String getTime( Date target ) {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM.dd");
String date = sdf.format( target );
return date;
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}
class Student {
private String name;
private Date birthDay;
private Integer mark;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Date getBirthDay() {
return birthDay;
}
public void setBirthDay(Date birthDay) {
this.birthDay = birthDay;
}
public Integer getMark() {
return mark;
}
public void setMark(Integer mark) {
this.mark = mark;
}
public Student(){
}
public Student(String name,Date birthDay , Integer mark){
this.name = name;
this.birthDay = birthDay;
this.mark = mark;
}
}
Q4: java随机分配！比如有五个座位a, b, c ,d ,e，有五个学生1,2,3,4,5 把学生分配到座位上不能有重复！求代码
import java.util.*;
public class a {
public static void main(String[] args) {
int i;
char c;
String[] a = {"座位1","座位2","座位3","座位4","座位5"};
/*生成座位list*/
ListString seat = new ArrayListString();
/*向其中添加座位*/
for(i = 0;i 5;i++){
seat.add(a[i]);
}
/*调用函数，将顺序打乱*/
Collections.shuffle(seat);
/*显示结果*/
for(i = 0,c = 'a'; c = 'e';c++,i++){
System.out.println("学生"+c+"坐在"+seat.get(i));
}
}
}
有问题追问我
Q5: 用java.EE编写计算器程序代码
java EE是java企业级开发平台的意思，实在是看不出跟计算器这种小程序有什么关联。不知道楼主要找的是不是这个。
package ex1;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JCheckBoxMenuItem;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JRadioButtonMenuItem;
import javax.swing.JTextField;
public class Calcutor extends JFrame {
private JTextField tf;
private JPanel panel1, panel2, panel3, panel4;
private JMenuBar myBar;
private JMenu menu1, menu2, menu3;
private JMenuItem editItem1, editItem2, help1, help2, help3;
private JRadioButtonMenuItem seeItem1, seeItem2;//单选框
private JCheckBoxMenuItem seeItem3;//复选框
private ButtonGroup bgb;
private String back;
private boolean IfResult = true, flag = false;
private String oper = "=";
private double result = 0;
private Num numActionListener;
private DecimalFormat df;
public Calcutor(){
super("科学计算器");//设置标题栏
df = new DecimalFormat("#.####");//保留四位小数
this.setLayout(new BorderLayout(10, 5));
panel1 = new JPanel(new GridLayout(1, 3, 10, 10));
panel2 = new JPanel(new GridLayout(5, 6, 5, 5));//5行6列
panel3 = new JPanel(new GridLayout(5, 1, 5, 5));
panel4 = new JPanel(new BorderLayout(5, 5));
/**
* 菜单栏
*/
myBar = new JMenuBar();
menu1 = new JMenu("编辑(E)");
menu2 = new JMenu("查看(V)");
menu3 = new JMenu("帮助(H)");
menu1.setFont(new Font("宋体", Font.PLAIN, 12));
menu2.setFont(new Font("宋体", Font.PLAIN, 12));
menu3.setFont(new Font("宋体", Font.PLAIN, 12));
/**
* 编辑栏
*/
editItem1 = new JMenuItem("复制(C) Ctrl+C");
editItem2 = new JMenuItem("粘贴(P) Ctrl+V");
editItem1.setFont(new Font("宋体",Font.PLAIN,12));
editItem2.setFont(new Font("宋体",Font.PLAIN,12));
/**
* 查看栏
*/
seeItem1 = new JRadioButtonMenuItem("科学型(T)");
seeItem2 = new JRadioButtonMenuItem("标准型(S)");
seeItem3 = new JCheckBoxMenuItem("数字分组(I)");
seeItem1.setFont(new Font("宋体",Font.PLAIN,12));
seeItem2.setFont(new Font("宋体",Font.PLAIN,12));
seeItem3.setFont(new Font("宋体",Font.PLAIN,12));
/**
* 帮助栏
*/
help1 = new JMenuItem("帮助主题(H)");
help2 = new JMenuItem("关于计算器(A)");
help1.setFont(new Font("宋体",Font.PLAIN,12));
help2.setFont(new Font("宋体",Font.PLAIN,12));
bgb = new ButtonGroup();//选项组
menu1.add(editItem1);
menu1.add(editItem2);
menu2.add(seeItem1);
menu2.add(seeItem2);
menu2.addSeparator();//添加一条分割线
menu2.add(seeItem3);
menu3.add(help1);
menu3.addSeparator();//添加一条分割线
menu3.add(help2);
myBar.add(menu1);
myBar.add(menu2);
myBar.add(menu3);
this.setJMenuBar(myBar);
numActionListener = new Num();//实现数字监听
/**
* 文本域，即为计算器的屏幕显示区域
*/
tf = new JTextField();
tf.setEditable(false);//文本区域不可编辑
tf.setBackground(Color.white);//文本区域的背景色
tf.setHorizontalAlignment(JTextField.RIGHT);//文字右对齐
tf.setText("0");
tf.setBorder(BorderFactory.createLoweredBevelBorder());
init();//对计算器进行初始化
}
/**
* 初始化操作
* 添加按钮
*/
private void init(){
addButton(panel1, "Backspace", new Clear(), Color.red);
addButton(panel1, "CE", new Clear(), Color.red);
addButton(panel1, "C", new Clear(), Color.red);
addButton(panel2, "1/x", new Signs(), Color.magenta);
addButton(panel2, "log", new Signs(), Color.magenta);
addButton(panel2, "7", numActionListener, Color.blue);
addButton(panel2, "8", numActionListener, Color.blue);
addButton(panel2, "9", numActionListener, Color.blue);
addButton(panel2, "÷", new Signs(), Color.red);
addButton(panel2, "n!", new Signs(), Color.magenta);
addButton(panel2, "sqrt", new Signs(), Color.magenta);
addButton(panel2, "4", numActionListener, Color.blue);
addButton(panel2, "5", numActionListener, Color.blue);
addButton(panel2, "6", numActionListener, Color.blue);
addButton(panel2, "×", new Signs(), Color.red);
addButton(panel2, "sin", new Signs(), Color.magenta);
addButton(panel2, "x^2", new Signs(), Color.magenta);
addButton(panel2, "1", numActionListener, Color.blue);
addButton(panel2, "2", numActionListener, Color.blue);
addButton(panel2, "3", numActionListener, Color.blue);
addButton(panel2, "-", new Signs(), Color.red);
addButton(panel2, "cos", new Signs(), Color.magenta);
addButton(panel2, "x^3", new Signs(), Color.magenta);
addButton(panel2, "0", numActionListener, Color.blue);
addButton(panel2, "-/+", new Clear(), Color.blue);
addButton(panel2, ".", new Dot(), Color.blue);
addButton(panel2, "+", new Signs(), Color.red);
addButton(panel2, "tan", new Signs(), Color.magenta);
addButton(panel2, "%", new Signs(), Color.magenta);
addButton(panel2, "π", numActionListener, Color.orange);
addButton(panel2, "e", numActionListener, Color.orange);
addButton(panel2, "′″", new Signs(), Color.orange);
addButton(panel2, "=", new Signs(), Color.red);
JButton btns = new JButton("计算器");
btns.setBorder(BorderFactory.createLoweredBevelBorder());
btns.setEnabled(false);//按钮不可操作
btns.setPreferredSize(new Dimension(20, 20));
panel3.add(btns);//加入按钮
addButton(panel3, "MC", null, Color.red);
addButton(panel3, "MR", null, Color.red);
addButton(panel3, "MS", null, Color.red);
addButton(panel3, "M+", null, Color.red);
panel4.add(panel1, BorderLayout.NORTH);
panel4.add(panel2, BorderLayout.CENTER);
this.add(tf, BorderLayout.NORTH);
this.add(panel3, BorderLayout.WEST);
this.add(panel4);
pack();
this.setResizable(false);//窗口不可改变大小
this.setLocation(300, 200);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
/**
* 统一设置按钮的的使用方式
* @param panel
* @param name
* @param action
* @param color
*/
private void addButton(JPanel panel, String name, ActionListener action, Color color){
JButton bt = new JButton(name);
panel.add(bt);//在面板上增加按钮
bt.setForeground(color);//设置前景（字体）颜色
bt.addActionListener(action);//增加监听事件
}
/**
* 计算器的基础操作（+ - × ÷）
* @param x
*/
private void getResult (double x){
if(oper == "+"){result += x;}
else if(oper == "-"){result -= x;}
else if(oper == "×"){result *= x;}
else if(oper == "÷"){result /= x;}
else if(oper == "="){result = x;}
tf.setText(df.format(result));
}
/**
* 运算符号的事件监听
*/
class Signs implements ActionListener{
public void actionPerformed(ActionEvent e) {
/*
* 用ActionEvent对象的getActionCommand()方法
* 取得与引发事件对象相关的字符串
*/
String str = e.getActionCommand();
/* sqrt求平方根 */
if(str.equals("sqrt")){
double i = Double.parseDouble(tf.getText());
if(i=0){
/*
* String.valueOf() 转换为字符串
* df.format() 按要求保留四位小数
* Math.sqrt() 求算数平方根
*/
tf.setText(String.valueOf(df.format(Math.sqrt(i))));
}
else{
tf.setText("负数不能开平方根");
}
}
/* log求常用对数 */
else if(str.equals("log")){
double i = Double.parseDouble(tf.getText());
if(i0){
tf.setText(String.valueOf(df.format(Math.log(i))));
}else{
tf.setText("负数不能求对数");
}
}
/* %求百分比 */
else if(str.equals("%")){
tf.setText(df.format(Double.parseDouble(tf.getText()) / 100));
}
/* 1/x求倒数 */
else if(str.equals("1/x")){
if(Double.parseDouble(tf.getText()) == 0){
tf.setText("除数不能为零");
}else{
tf.setText(df.format(1 / Double.parseDouble(tf.getText())));
}
}
/* sin求正弦函数 */
else if(str.equals("sin")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(df.format(Math.sin(i))));
}
/* cos求余弦函数 */
else if(str.equals("cos")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(df.format(Math.cos(i))));
}
/* tan求正切函数 */
else if(str.equals("tan")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(df.format(Math.tan(i))));
}
/* n!求阶乘 */
else if(str.equals("n!")){
double i = Double.parseDouble(tf.getText());
if((i%2==0)||(i%2==1))//判断为整数放进行阶乘操作
{
int j = (int)i;//强制类型转换
int result=1;
for(int k=1;k=j;k++)
result *= k;
tf.setText(String.valueOf(result));
}
else
{
tf.setText("无法进行阶乘");
}
}
/* x^2求平方 */
else if(str.equals("x^2")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(df.format(i*i)));
}
/* x^3求立方 */
else if(str.equals("x^3")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(df.format(i*i*i)));
}
/* ′″角度转换 */
/**
* 将角度值转换成弧度值，方便三角函数的计算
*/
else if(str.equals("′″")){
double i = Double.parseDouble(tf.getText());
tf.setText(String.valueOf(i/180*Math.PI));
}
else{
if(flag){
IfResult = false;
}
if(IfResult){
oper = str;
}else{
getResult(Double.parseDouble(tf.getText()));
oper = str;
IfResult = true;
}
}
}
}
/**
* 清除按钮的事件监听
*/
class Clear implements ActionListener{
public void actionPerformed(ActionEvent e) {
/*
* 用ActionEvent对象的getActionCommand()方法
* 取得与引发事件对象相关的字符串
*/
String str = e.getActionCommand();
if(str == "C"){
tf.setText("0");
IfResult = true;
result = 0;
}else if(str == "-/+"){
double i = 0 - Double.parseDouble(tf.getText().trim());
tf.setText(df.format(i));
}else if(str == "Backspace"){
if(Double.parseDouble(tf.getText()) 0){
if(tf.getText().length() 1){
tf.setText(tf.getText().substring(0, tf.getText().length() - 1));
//使用退格删除最后一位字符
}else{
tf.setText("0");
IfResult = true;
}
}else{
if(tf.getText().length() 2){
tf.setText(tf.getText().substring(0, tf.getText().length() - 1));
}else{
tf.setText("0");
IfResult = true;
}
}
}else if(str == "CE"){
tf.setText("0");
IfResult = true;
}
}
}
/**
* 数字输入的事件监听
*/
class Num implements ActionListener{
public void actionPerformed(ActionEvent e) {
String str = e.getActionCommand();
if(IfResult){
tf.setText("");
IfResult = false;
}
if(str=="π")
{
tf.setText(String.valueOf(Math.PI));
}
else if(str=="e")
{
tf.setText(String.valueOf(Math.E));
}
else{
tf.setText(tf.getText().trim() + str);
if(tf.getText().equals("0")){
tf.setText("0");
IfResult = true;
flag = true;
}
}
}
}
/**
* 小数点的事件监听
*/
class Dot implements ActionListener{
public void actionPerformed(ActionEvent e) {
IfResult = false;
if(tf.getText().trim().indexOf(".") == -1){
tf.setText(tf.getText() + ".");
}
}
}
/**
* main方法
*/
public static void main(String[] args) {
new Calcutor().setVisible(true);
}
}
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