1：正则表达式

public static void main(String[] args) {

　　String str = "123456456456456456";

　　boolean isNum = str.matches("[0-9]+");

　　System.out.println(isNum);

}

2：用类型转换

public static void main(String[] args) {

boolean bool = isNum("123456");

boolean bool2 = isNum("12b");

boolean bool3 = isNum("1234");

boolean bool4 = isNum("12345%8");

System.out.println(bool);

System.out.println(bool2);

System.out.println(bool3);

System.out.println(bool4);

}

private static boolean isNum(String str) {

try {

int num = Integer.valueOf(str);// 把字符串强制转换为数字

return true;// 如果是数字，返回True

} catch (Exception e) {

return false;// 如果抛出异常，返回False}

}

}