Java实现-每天三道剑指Offre(2-4)

实现一个单例模式

/**
 * 面试题2：实现单例模式
 * 
 * @author qiuyong 饿汉式
 */
public class Singleton01 {
    private Singleton01() {
    }

    private static Singleton01 instance = new Singleton01();

    public static Singleton01 getInstance() {
        return instance;
    
    }
}

/**
 * 面试题2:懒汉式
 * @author qiuyong
 */
public class Singleton02 {
    
    public static Singleton02 instance;
    
    public synchronized static Singleton02 getInstance(){
        if(null==instance){
            instance=new Singleton02();
        }        
        return instance;
    }

}

/**
 * 面试题2:利用内部类
 * @author qiuyong
 */
public class Singleton03 {
    
    public static Singleton03 getInstance(){
        return  InnerClass.instatnce;
    }
    
    private static class InnerClass{
        public static Singleton03 instatnce=new Singleton03();
    }
}

二维数组的查找

　　题目描述：一个二维数组，每一行从左到右递增，每一列从上到下递增．输入一个二维数组和一个整数，判断数组中是否含有整数。

public class Test {
    public static boolean find(int [][] arry,int num){
        int column=arry[0].length-1;
        int row=0;
        while(row<arry.length&&column>=0){
            if(num==arry[row][column]){
                return true;
            }
            if(arry[row][column]>num){
                column--;
            }else{
                row++;
            }
    }
    </span><span style="color: #0000ff;">return</span> <span style="color: #0000ff;">false</span><span style="color: #000000;">;
}

</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
    </span><span style="color: #0000ff;">int</span> [][] arry=<span style="color: #0000ff;">new</span> <span style="color: #0000ff;">int</span>[3][3<span style="color: #000000;">];
    </span><span style="color: #0000ff;">for</span>(<span style="color: #0000ff;">int</span> i=0;i&lt;arry.length;i++<span style="color: #000000;">){
        </span><span style="color: #0000ff;">for</span>(<span style="color: #0000ff;">int</span> j=0;j&lt;arry[0].length;j++<span style="color: #000000;">){
            arry[i][j]</span>=(i+1)*(j+1<span style="color: #000000;">);
        }
    }
    
    System.out.println(</span>"查看是否有元素9:"+find(arry,9<span style="color: #000000;">));
    System.out.println(</span>"查看是否有元素9:"+find(arry,0<span style="color: #000000;">));
}

}

替换空格

　　题目描述：请实现一个函数，把字符串中的每个空格替换成“%20”。

public class ReplaceBlank {
    public static void main(String[] args) {
        String str="i am happy";
        str=replaceBlank(str);
        System.out.println(str);
    }
    
    
    public static String replaceBlank(String str){
        if(null==str){
            return null;
        }
        StringBuffer sb=new StringBuffer();
        for(int i=0;i<str.length();i++){
            if(str.charAt(i)==' '){
                sb.append("%20");
            }else{
                sb.append(str.charAt(i));
            }
        }
        return sb.toString();
    }

}