反转字符串

 

public static void main(String[] args) { 
        String str = "just do it"; 
        //新建一个char数组,长度为str的长度+1 
        char [] c = new char[str.length()+1]; 
        //定义两个变量用来保存每次截取的起始长度到末尾长度 
        int j = str.length();       //开始截取的下标 
        int k = str.length();       //截取的末尾下标 
        int cIndex = 0; 
        for(int i = str.length()-1;i>=0; i--){ 
            if(str.charAt(i)== ' '|| i==0){ 
                if(i!=0){ 
                    j = i+1; 
                }else{ 
                    j = i; 
                } 
                while(j<k){ 
                    c[cIndex] = str.charAt(j); 
                    j++; 
                    cIndex++; 
                } 
                //一个单词存进char数组后,让后面一个值置空 
                c[cIndex++] = ' '; 
                //把末尾的值变为倒数第二个单词的下标 
                k = i; 
            } 
        } 
        System.out.println(new String(c)); 
    }