The third test report && learning summary

Application third experiment String 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).

The number of letters in the string s occurs statistics.
Code:

public class Wrold{
    public static void main(String[] args) {
        String str="this is a test of java";
        int count=0;
        for(int i=0;i<str.length();i++) {
            if(str.charAt(i)=='s')
                count++;
        }
        System.out.println("字符串里面“s”出现的次数："+count);
    }
}

Screenshot:

The string neutron count the number of times the string "is" appears.

Code:

public class Wrold{
    public static void main(String[] args) {
        String str="this is a test of java";
        int count=0;
        for(int i=0;i<str.length();i++) {
            if(str.charAt(i)=='i'&&str.charAt(i+1)=='s')
                count++;
        }
        System.out.println("字符串中子串“is”出现的次数："+count);
    }
}

Screenshot:

The number of words in the string "is" appears in the statistics.

Code:

public class Wrold{
    public static void main(String[] args) {
        String str="this is a test of java";
        String s[]=str.split(" ");
        int count=0;
        for(int i=0;i<s.length;i++) {
            if(s[i].equals("is"))
                count++;
        }
        System.out.println("该字符串中单词“is”出现的次数："+count);
    }
}

Screenshot:

Achieve reverse the string is output.

Code:

public class Wrold{
    public static void main(String[] args) {
        StringBuffer n=new StringBuffer();
        n.append("this is a test of java");
        String str=n.reverse().toString();
        System.out.println(str);
    }
}

Screenshot:

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.

Code:

public class Wrold{
    public static void main(String[] args){
        String str="123456";
        Scanner sc=new Scanner(System.in);
        String str=sc.nextLine();
        char m[]=str.toCharArray();
        char n[]=new char[50];int j=0;
        for(int i = m.length-3;i<m.length;i++) {
                n[j]=m[i];
                j++;
        }
        for(int i=0;i<m.length-3;i++){
            n[j]=m[i];
            j++;
        }
            System.out.print(n);
    
     }
}

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.

Code:

public class Wrold{
    public static void main(String[] args) {
        String str="ddejidsEFALDFfnef2357 3ed";
        int a=0, b=0, c=0;
        for(int i=0;i<str.length();i++) {
            if(str.charAt(i)>=70&&str.charAt(i)<=95) {
                a++;
            }
            else if(str.charAt(i)>=70&&str.charAt(i)<=100) {
                b++;
            }
            else
                c++;
        } 
        System.out.println ( "number of uppercase letters:" + A); 
        System.out.println ( "Number lowercase letters:" + B); 
        System.out.println ( "Number of non-English letters:" + C) ; 
    } 

}

Screenshot:

Learning Summary: The first part of this experiment is to use the string class, the teacher in class most of all speak, and I took a map. The second question, do not run out, I think the program should be no problem

the difference between this and super keywords:

this: current object

super: direct parent object

this (): constructor with no arguments current class, there may specify parameters, such as: this (a)

super (): constructor with no arguments direct parent class may be assigned a reference such as: super (a)

Note: 1, when calling a variable b in the method, the compiler will traverse upwards until you find the nearest one reference variable: b-> this.b-> super.b, if not found, the compiler will prompt an explicit error message;

2, when the variable b is defined only occurs when the parent class, then b = this.b = super.b;

3, when the cover member variable local variable b b, using this.b call a member variable, in this case include member variables and new subclass inherits variables, does not contain hidden variables;

4, when the sub-class member variables b b covering the parent class member variables, use super.b call this the hidden member variables;

5, when the child class overrides a superclass method Method (), you may be used super.method () to call the parent class's method is hidden;

6, super () and this () with hard conditions, or the compiler can not must be the first statement in a constructor by --Constructor call. That

Both appear to be the position of the first line constructor.

Inheritance: Java class allows only single inheritance.

Overloading and covering:

169 books.

The third test report && learning summary

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