方法动手动脑及实验

一。SquareInt.java    

  public class SquareInt {

  public static void main(String[] args) {
  int result;

  for (int x = 1; x <= 10; x++) {
  result = square(x);
  // Math库中也提供了求平方数的方法
  // result=(int)Math.pow(x,2);
  System.out.println("The square of " + x + " is " + result + "\n");
  }
  }

  // 自定义求平方数的静态方法
  public static int square(int y) {
  return y * y;
  }
  }

  结果截图:

二。RandomInt.java

  import javax.swing.JOptionPane;

  public class RandomInt {
  public static void main( String args[] )
  {
  int value;
  String output = "";

  for ( int i = 1; i <= 20; i++ ) {
  value = 1 + (int) ( Math.random() * 6 );
  output += value + " ";

  if ( i % 5 == 0 )
  output += "\n";
  }

  JOptionPane.showMessageDialog( null, output,
  "20 Random Numbers from 1 to 6",
  JOptionPane.INFORMATION_MESSAGE );

  System.exit( 0 );
  }
  }

  结果截图:

三。RollDie.java

  

  import javax.swing.*;

  public class RollDie {
  public static void main( String args[] )
  {
  int frequency1 = 0, frequency2 = 0,
  frequency3 = 0, frequency4 = 0,
  frequency5 = 0, frequency6 = 0, face;

  // summarize results
  for ( int roll = 1; roll <= 6000; roll++ ) {
  face = 1 + (int) ( Math.random() * 6 );

  switch ( face ) {
  case 1:
  ++frequency1;
  break;
  case 2:
  ++frequency2;
  break;
  case 3:
  ++frequency3;
  break;
  case 4:
  ++frequency4;
  break;
  case 5:
  ++frequency5;
  break;
  case 6:
  ++frequency6;
  break;
  }
  }

  JTextArea outputArea = new JTextArea( 7, 10 );

  outputArea.setText(
  "Face\tFrequency" +
  "\n1\t" + frequency1 +
  "\n2\t" + frequency2 +
  "\n3\t" + frequency3 +
  "\n4\t" + frequency4 +
  "\n5\t" + frequency5 +
  "\n6\t" + frequency6 );

  JOptionPane.showMessageDialog( null, outputArea,
  "Rolling a Die 6000 Times",
  JOptionPane.INFORMATION_MESSAGE );
  System.exit( 0 );
  }
  }

  结果截图:

四。编写一个算法,使用有以上算法生成指定数目(比如1000个)的随机整数。

  代码:

import java.util.*;
public class TextRandom {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner in = new Scanner(System.in);
        
        int a = (int)Math.pow(7,5);
        int m = (int)Math.pow(2, 31) - 1;
        int c = 0;
        
        System.out.print("请输入要产生随机数的个数:");
        int n = in.nextInt();
        for(int i = 0;i<n;i++)
        {
            Random x1 = new Random();
                int x3 = x1.nextInt(10);
                int x2 = (a* x3+c)%m;
               System.out.println(x2);
        }
    }

}

五。VariableArgumentsTest.java

  import java.awt.*;

  import java.awt.event.*;
  import java.util.*;


  public class VariableArgumentsTest{

  public static double max(double...values)
  {
  double largest=Double.MIN_VALUE;
  for (double v:values)
  if(v>largest) largest=v;
  return largest;
  }

  public static void main(String args[]) {

  System.out.println("Max:"+max(1,11,300,2,3));

  }
  }

  结果截图:

六。观察一下代码,你发现有什么特殊之处吗?  

  public class MethodOverload {

  public static void main(String[] args) {
  System.out.println("The square of integer 7 is " + square(7));
  System.out.println("\nThe square of double 7.5 is " + square(7.5));
  }

  public static int square(int x) {
  return x * x;
  }

  public static double square(double y) {
  return y * y;
  }
  }

  特殊之处:方法名相同,返回值类型和参数类型不同,输入需要进运算的参数会执行其相应类型的运算。

 七。CalculateN.java  

  import java.math.BigInteger;
  import java.util.Scanner;


  public class CalculateN {

  /**
  * @param args
  */
  public static void main(String[] args) {
  System.out.print("请输入N:");
  Scanner scanner=new Scanner(System.in);
  int number=scanner.nextInt();
  System.out.println(number+"!="+calculateN2(number));

  }

  public static long calculateN(int n) {
  if(n==1 || n==0){
  return 1;
  }

  return n*calculateN(n-1);
  }

  public static BigInteger calculateN2(int n) {
  if(n==1 || n==0){
  return BigInteger.valueOf(1);
  }
  return BigInteger.valueOf(n).multiply(calculateN2((n-1)));
  }
  }

  结果截图:

八。用阶乘来求组合数

  1.代码:

  

  import java.util.*;
  public class JC {

  public static void main(String[] args) {
  // TODO Auto-generated method stub
  Scanner in = new Scanner(System.in);
  System.out.print("请输入n:");
  int n = in.nextInt();
  System.out.print("请输入k:");
  int k = in.nextInt();
  int C = Jc(n)/(Jc(k)*Jc(n - k));
  System.out.println("C(n,k) = "+C);
  }
  public static int Jc(int n)//递归法计算阶乘
  {
  int s = 0;
  if(n < 0)
  System.out.println("Error!");
  else if(n == 1||n == 0)
  s = 1;
  else
  s = n * Jc(n -1);
  return s;
  }
  }

   2.结果截图:

        

九。使用递推的方法使用杨辉三角形计算

  1.代码:

  

  import java.util.Scanner;

  public class YH {

  public static void main(String[] args) {
  // TODO Auto-generated method stub
  Scanner in = new Scanner(System.in);
  System.out.print("请输入n:");
  int n = in.nextInt();
  System.out.print("请输入k:");
  int k = in.nextInt();

  int C = Yh(n,k);
  System.out.println("C(n,k) = "+C);
  }
  public static int Yh(int n,int k)
  {
  if(k == 0||n == k) return 1;
  int s=Math.min(k,n-k);
  int p = 1,q = 0;

  for(int i = 1; i <= s; i++)
  {
  q = p * (n-i+1)/(i);
  p = q;
  }

  return q;
  }
  }

  2.实验截图:

        

十。用组合数递推公式

  1.代码:

  

  import java.util.Scanner;

  public class DT {

  public static void main(String[] args) {
  // TODO Auto-generated method stub
  Scanner in = new Scanner(System.in);
  System.out.print("请输入n:");
  int n = in.nextInt();
  System.out.print("请输入k:");
  int k = in.nextInt();

  int C = Dt(n,k);
  System.out.println("C(n,k) = "+C);
  }
  public static int Dt(int n,int k)
  {
  int c = 0;
  if(n == 1||k == 0||n == k)
  c = 1;
  else
  c = Dt(n - 1,k - 1) + Dt(n - 1,k);
  return c;
  }
  }

  2.结果截图:

    

 

十一。汉诺塔问题

  1.代码:

  

  import javax.swing.JOptionPane;
  public class T3 {

  public static void main(String[] args) {
  // TODO Auto-generated method stub
  String str = JOptionPane.showInputDialog("输入汉诺塔层数:");
  int n = Integer.parseInt(str);

  JOptionPane.showMessageDialog(null, "挪动次数为"+fun(n));
  }
  public static int fun(int n){
  int count = 0;
  if(n == 1){
  count = 1;
  }
  else if(n == 2){
  count = 3;
  }

  else

  {
  count = 2*fun(n-1)+1;
  }
  return count;
  }
  }

  2.结果截图:

  

  

十二。判断字符串是否为回文数

  1.代码:

  import java.util.*;
  public class HW {

  public static void main(String[] args) {
  // TODO Auto-generated method stub
  String temp = "";
  char[] a;
  Scanner in = new Scanner(System.in);
  System.out.print("请输入要判断的字符串:");
  String str = in.next();
  a = str.toCharArray();//将字符串对象中的字符转换为一个字符数组
  for(int i = a.length - 1;i >= 0;i--)//将字符串逆置
  {
  temp += a[i];
  }
  if(str.equals(temp))
  System.out.println(str+"是回文数!");
  else
  System.out.println(str+"不是回文数!");
  }
  }

  2.结果截图:

          

 

posted @ 2016-10-13 22:19  IT瘦子  阅读(166)  评论(0编辑  收藏  举报