[刷题练习]实现函数 atoi 。函数的功能为将字符串转化为整数

【JDK1.8】

import java.util.*;

import java.math.BigInteger;

 

 

public class Solution {

    /**

     *

     * @param str string字符串

     * @return int整型

     */

    public int atoi (String str) {

              String strInt="" ;// write code here

        int intRe = 0;

        str = str.trim();

        for(int i = 0 ; i< str.trim().length();i++){

            strInt  = strInt + str.charAt(i);

            System.out.println(strInt);

            if(i== 0 && (str.charAt(i)== '+' || str.charAt(i)== '-'  ) ){

                continue;

            }

 

            try{

                if((new BigInteger(strInt)).compareTo(new BigInteger(String.valueOf(Integer.MAX_VALUE))) >0 ) {

                    intRe = Integer.MAX_VALUE;

                }else if( (new BigInteger(strInt)).compareTo(new BigInteger(String.valueOf(Integer.MIN_VALUE))) <0) {

                    intRe = Integer.MIN_VALUE;

                }else{

                    intRe = Integer.parseInt(strInt);

                }

 

            }catch(Exception e){

                e.printStackTrace();

            }

        }

        return intRe;

    }

}