java 面试编程题

前一段时间，面了大大小小n家公司，好多都有编程题，主要是看面试者的语言基本功，以及编程习惯。

package com.zhoubo;
/**
 * 用迭代的方法，判断是不是一个回文字符串，如”abdba”
 * @author BZ70000910
 *
 */
public class AbcbA {
	public static void main(String [] args){
		AbcbA instance = new AbcbA();
		System.out.println(instance.isAbcbA("abcefg"));
	}

	public boolean isAbcbA(String str){
		while(str.length() > 1){
			int length = str.length();
			char first = str.charAt(0);
			char last = str.charAt(length - 1);
			if(first == last){
				String strcpy = str.substring(1, length - 1);
				System.out.println(strcpy);				
				isAbcbA(strcpy);
			}else{
				return false;				
			}
			//不加break,就会进入死循环,因为退出循环也是一层一层的。做改错题肯定有意思。
			break;
		}
		return true;
	}
}

package com.zhoubo;
/**
 *如何用java读取大文件
 */
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class ReadBigFile {

	/**
	 * @param args
	 */
	public static void main(String[] args)throws Exception {
		//定义缓冲区的大小为1KB
		int bufSize = 1024;
		byte [] bs = new byte[bufSize];
		
		ByteBuffer byteBuffer = ByteBuffer.allocate(bufSize);
		FileChannel channel = new RandomAccessFile("c://dmmsi.log","r").getChannel();
		int size;
		//读取到输入流的最后
		while((size = channel.read(byteBuffer))!=-1){
			byteBuffer.rewind();
			byteBuffer.get(bs);
			System.out.println(new String(bs, 0, size));
			byteBuffer.clear();			
		}
		channel.close();
		
	}

}

package com.zhoubo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.CharBuffer;

/**
 * 读取字符串序列，如果有“abcd“，则返回true.
 * 提供一个每次读一个字符的函数
 * public char getChar()
 * @author BZ70000910
 *
 */
public class SimenseTest {
	static CharBuffer temp = CharBuffer.allocate(1024);

	/**
	 * @param args
	 */
	public static void main(String[] args)throws IOException {
		String str = "ABCD";
		InputStreamReader isr = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(isr);		
		br.read(temp);
		SimenseTest st = new SimenseTest();
		System.out.println(st.findString(str));

	}
	
	public char getChar()throws IOException{		
		temp.flip();
		char x = temp.get();
		temp.compact();
		return x;
	}

	public boolean findString(String str)throws IOException{
		char temp;
		int i = 0;
		while((temp = getChar())!=0){
//			System.out.println(temp);
			if(temp == str.charAt(i)){
				if(i == 3){
					return true;
				}else
					i++;
			}else
				i = 0;
			
		}
		return false;
	}
}

package com.zhoubo;
/**
 *编写一个class，提供void addElement(int element)方法，
 *提供int maxi()，提供int mini()，提供 int elementLength()，提供中间值int middle()
 */
import java.util.ArrayList;
import java.util.Arrays;

public class SimenseTest2 {
	private ArrayList<Integer> arrayList;
	
	public SimenseTest2(ArrayList<Integer> arrayList) {
		this.arrayList = arrayList;
	}

	public void addElement(int element){
		arrayList.add(element);
	}
	
	public int maxi(){
		int max = arrayList.get(0) ;
		for(int i = 1; i < arrayList.size(); i++){
			if(max < arrayList.get(i))
				max = arrayList.get(i);
		}
		return max;
	}
	
	public int mini(){
		int mini = arrayList.get(0);
		for(int i = 1; i < arrayList.size(); i++){
			if(mini > arrayList.get(i))
				mini = arrayList.get(i);
		}
		return mini;
	}
	
	public int length(){
		return arrayList.size();
	}
	
	public int middle(){
		int middle = 0;
		int size = arrayList.size();
		Integer [] array = (Integer [])arrayList.toArray(new Integer[size]);
		Arrays.sort(array);
		return array[size/2];
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		ArrayList<Integer> arrayList = new ArrayList<Integer>();
		SimenseTest2 st2 = new SimenseTest2(arrayList);
		st2.addElement(2);st2.addElement(3);st2.addElement(4);
		st2.addElement(5);st2.addElement(6);
		System.out.println(st2.maxi());
		System.out.println(st2.mini());
		System.out.println(st2.middle());
	}

}

package com.zhoubo;
/**
 *用stringtokenizer的方法，建立一个replace()方法
 */
import java.util.StringTokenizer;

public class StringReplace {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		StringReplace sr = new StringReplace();
		System.out.println("orilly ooh heolloo".replace('o', 'e'));
		System.out.println(sr.CharReplace('o', 'e', "orilly ooh heolloo"));

	}
	
	public String CharReplace(char oldChar, char newChar, String str){
		StringTokenizer stk = new StringTokenizer(str, Character.toString(oldChar));
		System.out.println(stk.countTokens());
		StringBuffer temp = new StringBuffer();
		//判断替换字符是否在开头
		if(str.charAt(0) == oldChar)
			temp.append(newChar);
		while(stk.hasMoreElements()){
			temp.append(stk.nextToken());
			temp.append(newChar);
		}
		//判断替换字符是否在结尾
		if(!(str.charAt(str.length()-1) == oldChar))
			temp.deleteCharAt(temp.length()-1);
		//如果多个重复的被替换
		return temp.toString();
	}

}

package com.zhoubo;
/**
 *提供一个字符串，转化成10进制输出，例如“AA”,输出170
 * @author BZ70000910
 *
 */
public class ZTETest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String str = "ABCDE" ;
		ZTETest test = new ZTETest();
		System.out.println(test.decimal(str));
	}

	public int decimal(String str){
		char [] chars;
		if(str != null){
			chars = str.toCharArray();
		}else
			chars = null;
		int sum = 0;
		int j = 0;
		for(int i = str.length()-1; i>=0 ; i--){
			sum = sum + (getValue(chars[i])<<(4*j));
			j++;
		}
		return sum;
	}
	
	public int getValue(char x){
		switch(x){
			case '0': return 0;
			case '1': return 1;
			case '2': return 2;
			case '3': return 3;
			case '4': return 4;
			case '5': return 5;
			case '6': return 6;
			case '7': return 7;
			case '8': return 8;
			case '9': return 9;
			case 'A': return 10;
			case 'B': return 11;
			case 'C': return 12;
			case 'D': return 13;
			case 'E': return 14;
			case 'F': return 15;
			default: return 0 ;
		}
	}
}

package com.zhoubo;
/**
 * 编写一个截取字符串的函数，输入为一个字符串和字节数，输出为按字节截取的字符串。
 *  但是要保证汉字不被截半个，如“我ABC”4，应该截为“我AB”，
 *  输入“我ABC汉DEF”，6，应该输出为“我ABC”而不是“我ABC+汉的半个”。
 * @author BZ70000910
 *
 */
public class ZTETest2 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String str = "我abc汉def";
		ZTETest2 test = new ZTETest2();
		System.out.println(str.substring(0,4));
		System.out.println(test.StringCutByByte(str, 2));

	}
	
	public String StringCutByByte(String str, int index){
		String temp = null;
		byte [] bytes = str.getBytes();
		byte [] bytetemp = new byte[index];
		for(int i=0; i<index ; i++ ){
			bytetemp[i] = bytes[i];
			System.out.println(bytes[i]);
		}
		if(index>1){
			if(bytes[index-1]<0&&bytes[index-2]>0){			
				//第三个参数表示要解码的字节数
				temp = new String(bytetemp,0,index-1);			
			}else{
				temp = new String(bytetemp);
			}		
		}else{
			if(bytes[index-1]<0){
				temp = null;
			}else
				temp = new String(bytetemp,0,1);
		}
		
		return temp;
	}

}