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：
