数组的使用

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格式化快捷键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("打开");        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相关的东西import java.util.*;public class BigIntegerTest //类名和文件名要相同{     public static void main(String[] args)  //主函数也就是入口函数   {        Scanner in = new Scanner(System.in); //键盘输入的对象      System.out.print("How many numbers do you need to draw? ");      int k = in.nextInt(); //获取数据，存入变量k中            System.out.print("What is the highest number you can draw? ");      int n = in.nextInt(); //获取数据，存入变量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!");//进行一些处理   }}

 稍微复杂的算法

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; //定义常量      final int NRATES = 6;      final int NYEARS = 10;      // set interest rates to 10 . . . 15%      double[] interestRate = new double[NRATES]; //新建数组      for (int j = 0; j < interestRate.length; j++)         interestRate[j] = (STARTRATE + j) / 100.0; //给数组赋值      double[][] balances = new double[NYEARS][NRATES]; //定义二维数组      // 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();      }   }}

 

同一个包下可以互相引用类，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, 你的年龄将会是 " + (age + 1));   }}

如何调整console字体大小？ 

打开window - preferences-- general - appearance - colors and fonts --debug - console font 就可以调节了。

 

我表示看不懂，这算法太复杂了，工作这么久，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; //定义常量      // allocate triangular array      int[][] odds = new int[NMAX + 1][]; //定义数组      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];  //定义一维数组      for (int i = 0; i < numbers.length; i++)         numbers[i] = i + 1;//赋值      // 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); //排序数组      System.out.println("Bet the following combination. It'll make you rich!");      for (int r : result)         System.out.println(r);   }}