String str =" aa.png,a2.png,a3.png";

String[] arrayStr =new String[]{};

arrayStr = str.split(",");

List list = java.util.Arrays.asList(arrayStr);

String[] storeStr = list.toArray(new String[list.size()]);

public class SplitTest { 
 
  public static void main(String args[]) { 
 
    String str = "a1.png,a2.png,a3.png";// 原始字符串 
    String[] arrayStr = new String[] {};// 字符数组 
    List<String> list = new ArrayList<String>();// list 
 
    arrayStr = str.split(",");// 字符串转字符数组 
    list = java.util.Arrays.asList(arrayStr);// 字符数组转list 
    String[] storeStr = list.toArray(new String[list.size()]);// list转成字符数组 
 
    /* 输出字符数组的值 */ 
    for (String s : arrayStr) { 
      System.out.println(s); 
 
    } 
    System.out.println("-------------"); 
    /* 输出list值 */ 
    for (String s : list) { 
      System.out.println(s); 
 
    } 
    System.out.println("-------------"); 
 
    for (String s : storeStr) { 
      System.out.println(s); 
 
    } 
    System.out.println("-------------"); 
  } 
}