黑马Sting四道练习题

键盘输入一个数字并打乱其内容

package heima.Test08.Stringtest;import java.util.Random;
import java.util.Scanner;
//键盘输入一个数字并打乱其内容
public class Demo4 {public static void main(String[] args) {//键盘输入一个数字Scanner sc = new Scanner(System.in);String str = sc.next();System.out.println(rese(str));}//打乱数字public static String rese(String str) {//变成字符串char[]  charArray = str.toCharArray();for (int i = 0; i < charArray.length; i++) {char j = 0;j = charArray[i];//生成随机数字Random random = new Random();int n = random.nextInt(charArray.length);charArray[i] = charArray[n];charArray[n] = j;}//变回字符串并返回return new String(charArray);}
}

生成验证码 长度为5 包括四个字母 1个数字 数字位置随机

package heima.Test08.Stringtest;import java.util.Random;//生成验证码
//长度为5  包括四个字母 1个数字  数字位置随机
public class Demo05 {public static void main(String[] args) {String result = zimu()+number();System.out.println(ARR(result));}//打乱顺序public static String ARR(String N){char[] charArray = N.toCharArray();//生成随机数字Random random = new Random();int n = random.nextInt(charArray.length);char j = charArray[charArray.length - 1];charArray[charArray.length-1] = charArray[n];charArray[n] = j;//变回字符串并返回return new String(charArray);}//生成四个随机字母public static String zimu(){char[] arr = new char[52];for (int i = 0; i < arr.length; i++) {if (i < 26) {arr[i] = (char) (i + 97);} else {arr[i] = (char) (i + 65 - 26);}}for (int i = 0; i < arr.length; i++) {System.out.println(arr[i]);}String result = "";for (int i = 0; i < 4; i++) {Random random = new Random();int n = random.nextInt(arr.length);result +=arr[n];}return result;}//生成一个随机数字public static char number(){char[] arr = new char[9];for (int i = 0;i < 8 ; i++){arr[i] = (char) ('0' + i);}Random random = new Random();int n = random.nextInt(arr.length);return arr[n];}
}

给定两个以字符串形式来表示的非负整数，返回他们的乘积，并用字符串表示

package heima.Test08.Stringtest;
//给定两个以字符串形式来表示的非负整数，返回他们的乘积，并用字符串表示
public class Demo06 {public static void main(String[] args) {String sum1 = "123";String sum2 = "123";int sum3 = number(sum2);int sum4 = number(sum1);String result1 = reverse(sum3,sum4);System.out.println(result1);}
//将字符串转换为数字public static int number(String n) {int sum = 0;int sum1 = 0;char[] s1 = n.toCharArray();for (int i = 0; i < s1.length; i++) {sum1 = s1[i] - '0';sum1 = (sum * 10)+sum1;sum = sum1;}return sum;}//把它们的乘积再转换为字符并返回public static String reverse(int z,int c) {int sum = z*c;String s = ""+sum;return s;}
}

给你一个字符串，里面有若干个单词组成，中间由空格隔开，返回最后一个单词的长度

package heima.Test08.Stringtest;
//给你一个字符串，里面有若干个单词组成，中间由空格隔开，返回最后一个单词的长度
public class Demo07 {public static void main(String[] args) {String str = "Hello World";char[] charArray = str.toCharArray();System.out.println(arr(charArray));}//返回最后一个单词的长度public  static int arr(char[] str){int count = 0;for (int i = str.length-1; i >=0; i--) {if (str[i] == ' '){break;}else{count++;}}return count;}
}