判断格式是否为邮箱

public static void main(String[] args) {

// 判断格式是否为邮箱 1234@qq.com

Scanner scanner = new Scanner(System.in);

String email = scanner.next();

if (email.contains(“@”)) {

int index = email.indexOf(“@”);// 得到@的索引的位置

String start = email.substring(0, index);// 切出开始的字符串

boolean isLetterOrDight = true;

for (int i = 0; i < start.length(); i++) {
char ch = start.charAt(i);
if (!Character.isLetterOrDigit(ch)) {

isLetterOrDight = false;
break;
}

}
if (isLetterOrDight) {
System.out.println("开头是数字或字母");
// 判断中间
if (email.contains(".")) {
int PointIndex = email.indexOf(".");// 得到@的索引的位置
String middle = email.substring(index + 1, PointIndex);// 切出开始的字符串
boolean middleIsLetterOrDight = true;

for (int i = 0; i < middle.length(); i++) {
char ch = middle.charAt(i);
if (!Character.isLetterOrDigit(ch)) {
middleIsLetterOrDight = false;
break;
}

}
if(middleIsLetterOrDight){
if (email.endsWith(".com") || email.endsWith(".cn") || email.endsWith(".net")) {
System.out.println("是邮箱");
}

}
}

} else {
System.out.println("结尾不是。com 。cn .net");
System.out.println("不是邮箱");
}

}

}