[2019.8.19] learning algorithm records - integer reversal

Example 1:

Input: 123
Output: 321
Example 2:

Input: -123
Output: -321
Example 3:

Input: 120
Output: 21

Note:
Suppose we have an environment can store the 32-bit signed integer, then the value range [-2 ^ 31 ^ 31 -2 - 1] Please According to this hypothesis, if the reverse integer overflow it returns 0 .
Source: stay button (LeetCode)

class Solution {
    public int reverse(int x) {
        String origNum = String.valueOf(x);
        char[] charArr = origNum.toCharArray();
        String reverse = "";
        if(charArr[0] == '-'){
            reverse = "-";
            for(int i = charArr.length-1; i>0;i--){
            reverse += charArr[i]; 
            }
        }
        else{        
        for(int i = charArr.length-1; i>=0;i--){
            reverse += charArr[i]; 
        }
    }
        int num;
        try{
            num = Integer.parseInt(reverse);            
        }
        catch(Exception e){
            return 0;
        }
         num = Integer.parseInt(reverse);
            if(num<Math.pow(-2,31) || num>Math.pow(2,31) ){
                num = 0;
            }   
       return num; 
    }
}
    

Note :
1, various data conversion method
int String transfer method using:

int x；
String y = String.valueOf(x);

String turn int method:

int z = Integer.parseInt(y);

String to String array:

char[] charArray = y.toCharArray();

2, exception handling

try{
}
catch(Exception e){
//此处为对异常如何处理
//比如，遇见异常后，返回某个值
}

Common abnormalities

3, JAVA power calculation
31 -2 power:

Math.pow(-2,31)