Java (store)

Fifth week Course summary:

   

Third experiment  String application class

• Purpose
• Master the use of class String class;
• Learn to use JDK help documentation;
• Content Experiments

1. Known string: "this is a test of java" required to do the following requirements :( source code, the results screenshot).

• 1. count the number of letters in the string s appears.
• Experiments Source:
• public class text1 {
   public static void main(String[] args) {
          String str="this is a test of java";
          int count=0;
          char c[]=str.toCharArray();
          for(int i=0;i<c.length;i++){
              if(c[i]=='s'){
                  count++;
              }          
           }
          System.out.println("s出现了"+count+"次");
             
      }
  }
• Screenshot:
• 
• 2. statistics the number of occurrences of the string neutron string "is".
• Experiments Source:
• public class texe2 {
   public static void main(String[] args) {
          String str = "this is a test of java";
          int count = 0, index = 0;
          while (true) {
              int n = str.indexOf("is", index);
              if (n != -1) {
                  index = n + 1;
                  count++;
              } else {
                  break;
              }
          }
          Of System.out.print ( "IS appeared" + count + "times");
      }
  }
• Screenshot:
• 
• 3. count the number of words in the string "is" appears
• Experiments Source:
• public class text3 {
   public static void main(String[] args) {
          int count=0;
          String str="this is a test of java";
          String s[]=str.split(" ");
          for(int i=0;i<s.length;i++){
              if(s[i].equals("is")){
                  count++;       
              }
          }
          System.out.println(count);
      }
  }
• Screenshot:

。

 

 

• 4. The realization of the reverse output string.
• Experiments Source:
• public class text4 {
   public static void main(String[] args) {
          String str = "this is a test of java";
          char s[] = str.toCharArray();
          for (int i=s.length-1;i>=0;i--) {
              System.out.print(s[i]);
          }
      }
  }
• Screenshot:
• 
• Summary: class when the teacher basically for us to demonstrate through eclipse again, that is the basic operation of such a situation;

2. Write a program, using the following algorithm to encrypt or decrypt the English string input by the user. It requires source code, the results screenshot.

 

Experiments Source:

import java.util.*;
public class text1 {
 public static void main(String[] args) {
        System.out.print("输入一个字符串：");
        var scanner = new Scanner(System.in);
  String str1 = scanner.nextLine();
        System.out.println(str1);
        char c[] = str1.toCharArray();
        int ASCII;
        char c1;
        for (int i = 0; i < c.length; i++) {
            ASCII = c[i] + 3;
            // System.out.print(ASCII+" ");
            c1 = (char) ASCII;
            // System.out.print(c1+" ");
            String s = String.valueOf(c1);
            System.out.print(s);

        }

    }
}

Screenshot:

 

 

 3. Given the string "ddejidsEFALDFfnef2357 3ed". The output string in the number of capital letters, lowercase letters count, the number of non-English letters.

Experiments Source:

public class text1 {
 public static void main(String[] args) {
        String str = "adhadhahdhahhH 1231";
        char c[] = str.toCharArray();
        int count1 = 0, count2 = 0, count3 = 0;
        for (int i = 0; i < c.length; i++) {
            int n = (int) c[i];
            if (65 <= n && n <= 90) {
                count1++;
            } else if (97 <= n && n <= 122) {
                count2++;
            } else {
                count3++;
            }

        }
        System.out.println ( "number of uppercase letters:" + count1 is);
        System.out.println ( "Number lowercase letters:" count2 +);
        System.out.println ( "Number of non-English letters:" + count3);

    }
 
}

Screenshot:

 

 

 Lessons Learned:

form:

Inheritance (extends);

Overloaded and overridden methods difference:

Point of difference	Overload	Overwrite
word	Overloading	Overriding
definition	The same method name, the number of parameters of different types, or	Method name, parameter types, the return values ​​are all the same type
definition	I did not ask for permission	The method can not be overridden in a more restrictive permission
range	It occurs in a class	It occurred in succession

Use super keyword;

The final keyword: class & Attribute & Method;

..... ..... benefit

Plain and boring