數組的使用
package javaDemo;
import java.util.*;
/**
*
* @author Administrator
* @version 1.0
*
*
*/
public class test {
public static void main(String[] args)
{
String[] greeting = new String[3];
greeting[0] = "Welcome to Core Java";
greeting[1] = "by Cay Horstmann";
greeting[2] = "and Gary Cornell";
for (String g : greeting)
System.out.println(g);
}
}
eclipse格式化快捷鍵Ctrl+Shift+F
jFrame
package javaDemo;
/**
*
* @author Administrator
* @version 1.0
*
*
*/
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
/**
* A program for viewing images.
*/
public class ImageViewer {
public static void main(String[] args) {
JFrame frame = new ImageViewerFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}
/**
* A frame with a label to show an image.
*/
class ImageViewerFrame extends JFrame {
public ImageViewerFrame() {
setTitle("ImageViewer");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
// use a label to display the images
label = new JLabel();
add(label);
// set up the file chooser
chooser = new JFileChooser();
chooser.setCurrentDirectory(new File("."));
// set up the menu bar
JMenuBar menuBar = new JMenuBar();
setJMenuBar(menuBar);
JMenu menu = new JMenu("文件");
menuBar.add(menu);
JMenuItem openItem = new JMenuItem("打開");
menu.add(openItem);
openItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
// show file chooser dialog
int result = chooser.showOpenDialog(null);
// if file selected, set it as icon of the label
if (result == JFileChooser.APPROVE_OPTION) {
String name = chooser.getSelectedFile().getPath();
label.setIcon(new ImageIcon(name));
}
}
});
JMenuItem exitItem = new JMenuItem("退出");
menu.add(exitItem);
exitItem.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
System.exit(0);
}
});
}
private JLabel label;
private JFileChooser chooser;
private static final int DEFAULT_WIDTH = 400;
private static final int DEFAULT_HEIGHT = 500;
}
BigIntegerTest
package javaDemo; //首先要引入包
/**
* @version 1.20 2004-02-10
* @author Cay Horstmann
*
**/
import java.math.*; //引入一些math相關的東西
import java.util.*;
public class BigIntegerTest //類名和文件名要相同
{
public static void main(String[] args) //主函數也就是入口函數
{
Scanner in = new Scanner(System.in); //鍵盤輸入的對象
System.out.print("How many numbers do you need to draw? ");
int k = in.nextInt(); //獲取數據，存入變量k中
System.out.print("What is the highest number you can draw? ");
int n = in.nextInt(); //獲取數據，存入變量n中
/*
compute binomial coefficient
n * (n - 1) * (n - 2) * . . . * (n - k + 1)
-------------------------------------------
1 * 2 * 3 * . . . * k
*/
BigInteger lotteryOdds = BigInteger.valueOf(1);
for (int i = 1; i <= k; i++)
lotteryOdds = lotteryOdds
.multiply(BigInteger.valueOf(n - i + 1))
.divide(BigInteger.valueOf(i));
System.out.println("Your odds are 1 in " + lotteryOdds + ". Good luck!");//進行一些處理
}
}
稍微復雜的算法
package javaDemo; //首先要引入包
/**
@version 1.40 2004-02-10
@author CayHorstmann
*/
public class CompoundInterest
{
public static void main(String[] args)
{
final int STARTRATE = 10; //定義常量
final int NRATES = 6;
final int NYEARS = 10;
// set interest rates to 10 . . . 15%
double[] interestRate = new double[NRATES]; //新建數組
for (int j = 0; j < interestRate.length; j++)
interestRate[j] = (STARTRATE + j) / 100.0; //給數組賦值
double[][] balances = new double[NYEARS][NRATES]; //定義二維數組
// set initial balances to 10000
for (int j = 0; j < balances[0].length; j++)
balances[0][j] = 10000;
// compute interest for future years
for (int i = 1; i < balances.length; i++)
{
for (int j = 0; j < balances[i].length; j++)
{
// get last year's balances from previous row
double oldBalance = balances[i - 1][j];
// compute interest
double interest = oldBalance * interestRate[j];
// compute this year's balances
balances[i][j] = oldBalance + interest;
}
}
// print one row of interest rates
for (int j = 0; j < interestRate.length; j++)
System.out.printf("%9.0f%%", 100 * interestRate[j]);
System.out.println();
// print balance table
for (double[] row : balances)
{
// print table row
for (double b : row)
System.out.printf("%10.2f", b);
System.out.println();
}
}
}
同一個包下可以互相引用類，并使用其中方法
CompoundInterest comp = new CompoundInterest();
comp.main(args);
package javaDemo; //首先要引入包
/**
@version 1.10 2004-02-10
@author Cay Horstmann
*/
import java.util.*;
public class InputTest
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
// get first input
System.out.print("你叫什么名字? ");
String name = in.nextLine();
// get second input
System.out.print("你多大了? ");
int age = in.nextInt();
// display output on console
System.out.println("你好, " + name + ". 明年, 你的年齡將會是 " + (age + 1));
}
}
如何調整console字體大小？
打開window - preferences-- general - appearance - colors and fonts --debug - console font 就可以調節了。
我表示看不懂，這算法太復雜了，工作這么久，都不懂。
package javaDemo;
/**
@version 1.20 2004-02-10
@author Cay Horstmann
*/
public class LotteryArray
{
public static void main(String[] args)
{
final int NMAX = 5; //定義常量
// allocate triangular array
int[][] odds = new int[NMAX + 1][]; //定義數組
for (int n = 0; n <= NMAX; n++)
odds[n] = new int[n + 1];
// fill triangular array
for (int n = 0; n < odds.length; n++)
for (int k = 0; k < odds[n].length; k++)
{
/*
compute binomial coefficient
n * (n - 1) * (n - 2) * . . . * (n - k + 1)
-------------------------------------------
1 * 2 * 3 * . . . * k
*/
int lotteryOdds = 1;
for (int i = 1; i <= k; i++)
lotteryOdds = lotteryOdds * (n - i + 1) / i;
odds[n][k] = lotteryOdds;
}
// print triangular array
for (int[] row : odds)
{
for (int odd : row)
System.out.printf("%4d", odd);
System.out.println();
}
}
}
表示作者很牛逼。
/**
@version 1.20 2004-02-10
@author Cay Horstmann
*/
package javaDemo;
import java.util.*;
public class LotteryDrawing
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
System.out.print("How many numbers do you need to draw? ");
int k = in.nextInt();
System.out.print("What is the highest number you can draw? ");
int n = in.nextInt();
// fill an array with numbers 1 2 3 . . . n
int[] numbers = new int[n]; //定義一維數組
for (int i = 0; i < numbers.length; i++)
numbers[i] = i + 1;//賦值
// draw k numbers and put them into a second array
int[] result = new int[k];
for (int i = 0; i < result.length; i++)
{
// make a random index between 0 and n - 1
int r = (int) (Math.random() * n); //直接使用Math的random方法
// pick the element at the random location
result[i] = numbers[r];
// move the last element into the random location
numbers[r] = numbers[n - 1];
n--;
}
// print the sorted array
Arrays.sort(result); //排序數組
System.out.println("Bet the following combination. It'll make you rich!");
for (int r : result)
System.out.println(r);
}
}
Java 積累復習用
1.jvm 默認編碼:Java的默認編碼 2.jvm heap :?Java虛擬機的內存組成以及堆內存介紹 3.Java命令學習系列(一)--Jps 4.Java命令學習系列(二)--Jstack 5 ...
Selenium Webdriver java 積累一
Selenium Webdriver 學習: http://jarvi.iteye.com/category/203994 https://github.com/easonhan007/webdriv ...
java積累的細節問題
一.將幾個數字進行拼接,拼接成字符串 一定要將""放到幾個數字之前,否則就會把數字相加之后的數轉化成字符串 如你需要拼接年份,月份,和日 如果:2018+12+13+"& ...
【轉載】分享下多年積累的對JAVA程序員成長之路的總結
注:該文是從百度貼吧轉載過來,之前看到覺得寫得還不錯,對Java開發學習者來說很有意義的,可以看看. 我也搞了幾年JAVA了,由于一向懶惰,沒有成為大牛,只是一普通程序猿,不愛玩社交網站,不愛玩微博, ...
分享下多年積累的對JAVA程序員成長之路的總結
http://blog.csdn.net/zhongzelin/article/details/8643269我也搞了幾年JAVA了,由于一向懶惰,沒有成為大牛,只是一普通程序猿,不愛玩社交網站,不愛 ...
java 基礎導航
ecplise 常用快捷鍵 java notepad++ java封裝好處和原則 java1 基本概述和java環境變量配置 java2 基本概念介紹和基本關鍵字.基本數據類型 java3 基本流程語 ...
分享下對JAVA程序員成長之路的總結<;轉>;
我也搞了幾年JAVA了,由于一向懶惰,沒有成為大牛,只是一普通程序猿,手癢來給新人分享下從新手成長為老鳥的已見. ? 首先初識語法的階段,必須要學會怎么操作對象,操作if和for,操作list set ...
2019年京東Java研發崗社招面經(面試經歷+真題總結+經驗分享)！
本篇先以日歷形式回顧秋招之路,方便各位參考某廠的處理進度:然后是總結歸納春秋招Java面試題庫:最后做個總結還有展望,開始新的征程~ 面試經歷京東面試真題面試經驗分享1.面試經歷 2018年的冬季特別 ...
java學習大方向
總結Java程序員成長之路?? 轉載 ?http://bbs.javazhijia.com/topic/1bb0733f80d94aedb50cc3b66d9792b6.html 我也搞了幾年JAVA ...
隨機推薦
Android MMS 之APN
APN的英文全稱是Access Point Name,中文全稱叫接入點,是您在通過手機上網時必須配置的一個參數,它決定了您的手機通過哪種接入方式來訪問網絡.用來標識GPRS的業務種類,目前分為兩大類: ...
ListView之setEmptyView的問題
使用listView或者gridView時,當列表為空時,有時需要顯示一個特殊的empty view來提示用戶,一般情況下,如果你是繼承ListActivity,只要?
HDOJ --- 2196 Computer
Computer Time Limit: 1000/1000 MS (Java/Others)????Memory Limit: 32768/32768 K (Java/Others)Total Su ...
Phonegap 安卓的自動升級與更新。當版本為4.0的時候
清單文件中:
修改oracle內存
[oracle@bi11g bin]$ ./sqlplus /nolog SQL*Plus: Release 11.2.0.1.0 Production on Fri Dec 1618:39:36 2 ...
讀書時間《JavaScript高級程序設計》四：BOM，客戶端檢測
隔了一段時間,現在開始看第8章. 第8章:BOM BOM提供了很多對象,用于訪問瀏覽器的功能.BOM的核心對象是window,它表示瀏覽器的一個實例. window對象是通過javascript訪問瀏 ...
<;iOS開發>;之App上架流程(2017)
本文主要介紹了App上架流程,以及上架過程中會遇到的一些問題. 一.App上架前的準備. 上架前,需要開發人員有蘋果開發者賬號,具體請閱讀蘋果開發者賬號注冊申請流程.本文是在已經擁有開發者賬號的前提下 ...
asp.net緩存 (轉)
