Integer array converted to string, string converted to integer array, java language implementation

Convert a string to an array of integers.

public static int[] stringFormatInteger(String s) {
    	int len=s.length();
    	int[] a=new int[len];
    	for(int i=0;i<len;i++) {
    		a[i]=s.charAt(i)-'0';
    	}
    	return a;
    }

Convert an integer array to a string.

public static String integerFormatString(int[] a) {
    	
    	int len=a.length;
    	char[] ch=new char[len];
    	for(int i=0;i<len;i++) {
    		switch(a[i]) {
    		case 0:
    			ch[i]='0';break;
    		case 1:
    			ch[i]='1';break;
    		case 2:
    			ch[i]='2';break;
    		case 3:
    			ch[i]='3';break;
    		case 4:
    			ch[i]='4';break;
    		case 5:
    			ch[i]='5';break;
    		case 6:
    			ch[i]='6';break;
    		case 7:
    			ch[i]='7';break;
    		case 8:
    			ch[i]='8';break;
    		case 9:
    			ch[i]='9';break;
    			default:break;
    		}
    	}
    	String str=new String(ch);
    	return str;
    }