方法 实验报告

素数

import java.util.*;

public class PrimenumberManager {
    
    private int output_count=0;                        //记每行的输出数
    private int min = 3;
    private int max = 100;

    public void calculation(){                //计算范围内的素数
        System.out.println(min+"到"+max+"之间的素数有：");
        for( int i=min; i<=max; i++){
            int sign=0;                        //标记
            for( int j=2; (j<Math.sqrt(i))&&(sign==0); j++){
                if((i%j)==0){
                    sign++;
                }
            }
            if(sign==0){
                display(i);
            }
        }
        output_count = 0;
        System.out.println();
    }
    
    public void display( int number ){
        System.out.print(number);
        output_count++;
        if( output_count == 5){            //一行有五个数字，换行
            System.out.println();
            output_count=0;
        }
        else{
            System.out.print(" ");
        }
    }
    
    @SuppressWarnings("resource")
    public void setMinMax(){
        System.out.println("请输入两个整数");
        Scanner in = new Scanner( System.in );
        int min = in.nextInt();
        int max = in.nextInt();
        if( max < min){
            max+= min;
            min = max-min;
            max = max-min;
        }
        this.min = min;
        this.max = max;
        calculation();
    }
    
}

/*
 * 目的：计算范围内素数
 * 作者：刘雨馨
 * 日期：2018.10.14
 */
public class PrimeNumber {
    public static void main( String [] args ){
        PrimenumberManager p = new PrimenumberManager();
        p.calculation();
        p.setMinMax();
    }
}

回文

public class Detection {
    
    private int sign=0;
    private int length;
    private String str = new String();
    
    public void setStr( String str ){
        int n=0;
        this.str = str;
        length = str.length();
        judge(n);
    }
    
    public void judge( int n ){
        if((length-n)<=1){                //字符串是零或单个字符回文
            sign=1;
        }
        else{
            int front = str.charAt(n);
            int back = str.charAt(length-n-1);
            if( front == back ){
                judge(++n);
            }
            else{
                sign=0;
            }
        }
    }
    
    public void display(){
        if( sign == 0)
            System.out.println("该字符串不回文");
        else
            System.out.println("该字符串回文");
    }
    
}

import java.util.Scanner;

public class Palindrome {
    public static void main( String [] args ){
        Detection d = new Detection();
        @SuppressWarnings("resource")
        Scanner in = new Scanner( System.in );
        String str = new String();
        System.out.println("请输入字符串");
        str = in.next();
        d.setStr(str);
        d.display();
    }
}

单词频率

import java.io.*;

public class Statistics {
    
    private String word="";
    private String[] str = new String[500];
    private int[] count = new int[500];
    private int i=0;        //统计现有单词的数量
    
    //读取文件内容
    public void readFile( String filename ){
        File file = new File( filename );
        Reader reader = null;
        try{
            reader = new InputStreamReader( new FileInputStream( file ) );
            int tempchar;
            while((tempchar = reader.read()) != -1 ){
                extractWord( tempchar );                            //传每个字符
            }
            reader.close();
        }
        catch( Exception e ){
            e.printStackTrace();
        }
    }
    
    //提取单词
    public void extractWord( int tempchar ){
        if( ((tempchar>65&&tempchar<90)||(tempchar>97&&tempchar<122)) ){    //tempchar为字母时，追加
            word += (char)tempchar;
        }
        else if((!"".equals(word))){
            statisticalWord();                                                //统计
            word="";
        }
    }
    
    //统计单词
    public int statisticalWord(){
        int j=0;
        for( ; j<i; j++ ){
            if( str[j].equals(word) ){
                count[j]++;                                            //计次加一
                return 0;
            }
        }
        str[j]=word;                                                //添加单词
        count[j]++;
        i++;
        return 0;
    }
    
    //将统计信息显示
    public void display(){
        for(int j=0; j<i; j++ ){
            System.out.println(str[j]+"	"+count[j]);
        }
    }
    
}

public class Words {
    public static void main( String [] args ){
        String filename = "C:/file.txt";
        Statistics sta = new Statistics();
        sta.readFile(filename);
        sta.display();
    }
}