Java test report (three) and summary

Application third experiment String class

First, the purpose of the experiment

(1) using the master class String class;

(2) learn to use JDK help documentation;

Second, the experimental content

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 appears ① statistics.

The number of neutrons ② string string "is" appears in the statistics.

The number of words in the string "is" appears ③ statistics.

④ achieve reverse the string is output.

Experiment code:

package com.company;

public class Main {
    public static void main(String[] args){
        int count=0,count1=0,count2=0;
        String ch="this is a test of java";
        char[] c=ch.toCharArray();
        for(int i=0;i<c.length;i++){
            if(c[i]=='s'){
                count++;
            }
            if(c[i]=='i'&&c[i+1]=='s'){
                count1++;
                if(C [I-. 1] == '' && C [I + 2] == '' ) { 
                    count2 ++ ; 
                } 
            } 
        } 
        System.out.println ( "number of times the letter string s appears:" + COUNT) ; 
        System.out.println ( "number of occurrences:" "in the character string string" iS + count1 is); 
        System.out.println ( "number of occurrences:" "in the word string" iS + count2); 
        the System.out .print ( "reverse output string:" );
         for ( int I =-c.length. 1; I> = 0; i-- ) { 
            of System.out.print (C [I]); 
        } 
    } 
}

Output:

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.

Experiment code:

package com.company;

import java.util.Scanner;

class Main {
    public static void main(String[] args){
        Scanner n=new Scanner(System.in);
        String ch=n.next();
        char[] c=ch.toCharArray();
        for(int i=0;i<c.length;i++){
            c[i]+=3;
        }
        System.out.print("加密后的结果：");
        for(int i=0;i<c.length;i++){
            System.out.print(c[i]);
        }
    }
}

实验结果：

3.已知字符串“ddejidsEFALDFfnef2357 3ed”。输出字符串里的大写字母数，小写英文字母数，非英文字母数。

实验代码：

package com.company;

public class ovo {
    public static void main(String[] args){
        int count1=0,count2=0,count3=0;
        String ch="ddejidsEFALDFfnef2357 3ed";
        char[] c=ch.toCharArray();
        for(int i=0;i<c.length;i++){
            if(c[i]>='A'&&c[i]<='Z'){
                count1++;
            }
            else if(c[i]>='a'&&c[i]<='z'){
                count2++;
            }
            else {
                count3++;
            }
        }
        System.out.println("大写字母数："+count1);
        System.out.println("小写字母数："+count2);
        System.out.println("非英文字母数："+count3);
    }
}

实验结果：

小结：

final关键字是我们经常使用的关键字之一，它的用法有很多，但是并不是每一种用法都值得我们去广泛使用。它的主要用法有以下四种：

1、用来修饰数据，包括成员变量和局部变量，该变量只能被赋值一次且它的值无法被改变。对于成员变量来讲，我们必须在声明时或者构造方法中对它赋值；

2、用来修饰方法参数，表示在变量的生存期中它的值不能被改变；

3、修饰方法，表示该方法无法被重写；

4、修饰类，表示该类无法被继承。

上面的四种方法中，第三种和第四种方法需要谨慎使用，因为在大多数情况下，如果是仅仅为了一点设计上的考虑，我们并不需要使用final来修饰方法和类。

Java test report (three) and summary

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