JAVA学习之统计一个文件中各个字符出现次数

统计一个文件calcCharNum.txt中各个字符出现次数：A(8),B(16),C(10)...,a(12),b(10),c(3)....，括号内代表字符出现次数，要求按照出现次数从小到达排序输出。如果是回车符则按照空格符处理

先定义属性字符char ch;num为字符出现次数，没出现一次num加一

class CharNum{
	private char ch;
	private int num;
	public CharNum(char ch){
		this.ch=ch;
		this.num=1;
	}
	public void incr() {
		this.num++;
	}
	public char getCh() {
		return ch;
	}
	@Override
	public String toString() {
		return ch+"("+num+")";
	}
	public boolean big(CharNum charNum) {
		boolean res=false;
		if(this.num>charNum.num)
			res=true;
		else if(this.num==charNum.num)
			res=this.num>charNum.num;
		return res;
	}
	
}

将字符存入数组中用字符类CharNum定义数组，由于不确定字符个数需要统计个数的属性count；初始化数组长度为10

class ArrayList{
	private CharNum[] arr;
	private int count;
	public ArrayList() {
		this(10);
	}
	public ArrayList(int length) {
		arr=new CharNum[length];
	}

数组大小不确定需要数组自增放法

private void resize() {
		CharNum[] carr=new CharNum[arr.length*2];
		for(int i=0;i<count;i++) 
		     carr[i]=arr[i];
		this.arr=carr;
	}

搜索文件中的字符，将搜索到的字符的下标位置返回

private int exists(char ch) {
		int res=-1;
		for(int i=0;i<count;i++) {
		     CharNum cn=arr[i];
		     if(cn.getCh()==ch) {
			       res=i;
			       break;
		     }
		}
		return res;

得到返回位置后如果字符以及存在字符个数加一，字符不存在添加到数组内，数组自增

public void add(char ch) {
		int pos=exists(ch);
		if(pos>0)
			arr[pos].incr();
		else {
			arr[count++]=new CharNum(ch);
			if(count>=arr.length)
				resize();
		}
	}

根据字符的个数从小到大排序

public void sort() {
		for(int i=1;i<count;i++) {
			for(int k=0;k<count-i;k++) {
				if(arr[k].big(arr[k+1])) {
					CharNum tmp=arr[k];
					arr[k]=arr[k+1];
					arr[k+1]=tmp;
				}
			}
		}
	}

展示输出

public void show() {
		for(int i=0;i<count;i++)
			System.out.println(arr[i]+",");
	}

完整代码展示

public class Test2 {
//5、统计一个文件calcCharNum.txt中各个字符出现次数：A(8),B(16),C(10)...,
//a(12),b(10),c(3)....，括号内代表字符出现次数，要求按照出现次数从小到达排序输出
	public static void main(String[] args)throws Exception {
		ArrayList list=new ArrayList();
		try(Reader r=new FileReader("d:/data/in.txt")){
			int kk=-1;
			while(true) {
				kk=r.read();
				if(kk==-1)
					break;
				if(kk==
||kk==	||kk==
)
					kk= ;
				list.add((char)kk);
			}
			list.sort();
			list.show();
		}
	}
}
class CharNum{
	private char ch;
	private int num;
	public CharNum(char ch){
		this.ch=ch;
		this.num=1;
	}
	public void incr() {
		this.num++;
	}
	public char getCh() {
		return ch;
	}
	@Override
	public String toString() {
		return ch+"("+num+")";
	}
	public boolean big(CharNum charNum) {
		boolean res=false;
		if(this.num>charNum.num)
			res=true;
		else if(this.num==charNum.num)
			res=this.num>charNum.num;
		return res;
	}
	
}
class ArrayList{
	private CharNum[] arr;
	private int count;
	public ArrayList() {
		this(10);
	}
	public ArrayList(int length) {
		arr=new CharNum[length];
	}
	public void add(char ch) {
		int pos=exists(ch);
		if(pos>0)
			arr[pos].incr();
		else {
			arr[count++]=new CharNum(ch);
			if(count>=arr.length)
				resize();
		}
	}
	public void sort() {
		for(int i=1;i<count;i++) {
			for(int k=0;k<count-i;k++) {
				if(arr[k].big(arr[k+1])) {
					CharNum tmp=arr[k];
					arr[k]=arr[k+1];
					arr[k+1]=tmp;
				}
			}
		}
	}
	public void show() {
		for(int i=0;i<count;i++)
			System.out.println(arr[i]+",");
	}
	private void resize() {
		CharNum[] carr=new CharNum[arr.length*2];
		for(int i=0;i<count;i++) 
		     carr[i]=arr[i];
		this.arr=carr;
	}
	private int exists(char ch) {
		int res=-1;
		for(int i=0;i<count;i++) {
		     CharNum cn=arr[i];
		     if(cn.getCh()==ch) {
			       res=i;
			       break;
		     }
		}
		return res;
	}
}