JAVA语言程序设计课后习题----第六单元解析（仅供参考）

1　　本题就是基本函数的用法

 import java.util.Scanner;
 
 public class Poone {
 
     public static void main(String[] args) {
         Scanner input = new Scanner(System.in);
         System.out.println("请输入一个字符串:");
         String string = input.next();
         System.out.println("显示这个字符串:");
         System.out.println(string);
         System.out.println("这个字符串长度为:");
         System.out.println(string.length());
         System.out.println("该字符串第一个字符");
         System.out.println(string.charAt(0));
         System.out.println("该字符串最后一个字符:");
        // System.out.println(string.charAt(2));
         System.out.println(string.charAt(string.length()-1));
     }
 
 }

2　　String类中有一个方法 public boolean contains（Sting s）就是用来判断当前字符串是否含有参数指定的字符串

 import java.util.Scanner;
 
 public class Potwo {
     public static void main(String[] args) {
 
         Scanner input = new Scanner(System.in);
         System.out.println("请你输入第一个字符串:");
         String s1 = input.next();
         System.out.println("请你输入第二个字符串");
         String s2 = input.next();
         System.out.print("第二个字符串是否为第一个字符串的子串:");
         System.out.println(s1.contains(s2));
 
     }
 
 }

3　　判断书写格式是否合法，自行百度正则表达式

 import java.util.Scanner;
 
 public class Pothree {
     public static void main(String[] args) {
         String regex = "\\d{3}+-\\d+-\\d{3}+-\\d{5}+-\\d";
         //String a = "887-7-111-50690-4";
         System.out.println("请你输入一个字符串:");
         Scanner input = new Scanner(System.in);
         String a =input.next();
         if (a.matches(regex))
             System.out.println("该字符串合法");
         else
             System.out.println("该字符串不合法");
     }
 }

4　　定义一个在字母范围的条件即可

 import java.util.Scanner;
 
 public class Pofour {
     public static void main(String[] args) {
         Scanner input = new Scanner(System.in);
         System.out.println("请你输入一串字符串:");
         String s = input.next();
         System.out.print("字符串中字母的个数为:"+ countLetters(s));
     }
     public static int countLetters(String s){
         int count =0;
 //        字符串转数组
         char []A = s.toCharArray();
         for (int i = 0; i <A.length ; i++) {
             if (A[i]>='a'&&A[i]<='z'||A[i]>='A'&&A[i]<='Z')
                 count++;
         }
         return count;
     }
 }

5　　本题只要根据题目意思理解就行

 public class jinzhi {
     public static String toBinary(int value){
        String s ="";
         while (value!=0){
            s=value%2+s;
             value /= 2;
         }
 
         return s;
     }
 
     public static void main(String[] args) {
         System.out.println(toBinary(42));
     }
 
 }

6　　把字符串变成数组，然后根据冒泡法进行排序即可

 public class Posix {
     public static void main(String[] args) {
 
         System.out.println(sort("morning"));
     }
     public static String sort(String s){
         String string=new String();
 
         char []a=s.toCharArray();
         for (int i = 0; i <a.length-1 ; i++) {
             for (int j = i+1; j < a.length; j++) {
                 if (a[i]>a[j]){
                     a[i]^=a[j];
                     a[j]^=a[i];
                     a[i]^=a[j];
                 }
             }
         }
         for (int A:a)
             System.out.print((char)A+" ");
         return string;
     }
 }

7　　只要把对应的ascii值+1即可

 import java.util.Scanner;
 
 public class Poseven {
     public static void main(String[] args) {
         //System.out.println(');
         Scanner input = new Scanner(System.in);
         System.out.print("请输入一串字符串:");
         String string = input.next();
         char []A = string.toCharArray();
         System.out.print("该字符串的密文为:");
         for (int i = 0; i < A.length; i++) {
             if ((A[i]>='a'&&A[i]<='z'||A[i]>='A'&&A[i]<='Z'))
                 System.out.print((char)(A[i]+1));
             else
                 System.out.print(A[i]);
         }
     }
 }

8　　只要把对应的ascii值-1即可

import java.util.Scanner;
 
public class Poeight {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("请输入一串字符串：");
        String string = input.next();
        char []A = string.toCharArray();
        System.out.print("该字符串的明文为：");
        for (int i = 0; i < A.length; i++) {
            if ((A[i]>='a'&&A[i]<='z'||A[i]>='A'&&A[i]<='Z'))
                System.out.print((char)(A[i]-1));
            else
                System.out.print(A[i]);
        }
    }
}

9　　根据题目意思，在“ ”，“，”，“.”分割即可

 public class Ponine {
     public static void main(String[] args) {
         String s = "no pains,no gains.";
         int count=0;
 //        字符串变数组
         char[]A =s.toCharArray();
         char []B=new char[26];
         for (int AA:A){
             System.out.print((char)AA);
         }
         System.out.println();
       //  for (int i = 0; i <A.length ; i++) {
         int k=0;
            while (A[k]!='.') {
                if (A[k] == ' ' || A[k] == ',') {
                    k++;
                    System.out.println();
                    if (k == A.length)
                        k--;
                }
                System.out.print(A[k]);
                k++;
            }
      //   }
         System.out.println();
             int j=0;
         for (int i = 0; i <A.length ; i++)
             if (A[i] != ' ' && A[i] != ',' && A[i] != '.') {
                 B[j] = A[i];
                 j++;
                 count++;
             }
 
     }
 }

10　　熟悉cmd下执行java程序

11　　冒泡法进行排序

12、13  自行百度查看