Java 算法笔记

数字与字符串之间的相互转换

String  str = "123";
int num = 12;
//字符串转换为数字
int tranToNum = Integer.parseInt(str, 16);//这里的16表示十六进制，也可以是十进制或是其他进制(如果不写，这里默认是10进制)
System.out.println(tranToNum);
//数字串转化为字符串
String tranToStr = String.valueOf(num);
System.out.println(tranToStr);

从键盘接受输入的字符串

//第一种
@SuppressWarnings("resource")
Scanner sc =new Scanner(System.in);
String str=sc.next();
System.out.println(str);
//第二种
@SuppressWarnings("resource")
Scanner sc1=new Scanner(System.in);
String str1= sc1.nextLine();
System.out.println(str1);
//第三种
Reader reader =new InputStreamReader(System.in);
BufferedReader bReader =new BufferedReader(reader);
//上二同  BufferedReader bReader = new BufferedReader(new InputStreamReader(System.in));
try {
    String str2=bReader.readLine();
    System.out.println(str2);
} catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
//第四种
Scanner s = new Scanner(System.in);
int i = 0;
if(s.hasNextInt())   //算法题中，整数和字符串同
{
    i = s.nextInt();
}
s.close();//关闭scanner

除与取余

int i=123;
int a=i/100;  //a=1
int b=(i%100)/10; //b=2
int c=i%10;  //c=3