常用API-StringBuilder

package Java_project_1;

public class Test{
    public static void main(String[] args) {
        int[] arr1=null;
        System.out.println(toString(arr1));
        int[] arr2={10,88,99};
        System.out.println(toString(arr2));
    }
    public static String toString(int[] arr){
        if (arr!=null){
            StringBuilder sb=new StringBuilder("[");
            for (int i=0;i