How to solve NumberFormat exception in Java?

In Java, the NumberFormat exception is typically caused by a string not being able to be correctly parsed as a number. To resolve this exception, the following methods can be considered:

1. Use a try-catch statement to catch exceptions and handle them in the catch block. For example:

try {
    // 尝试解析字符串为数字
    double number = Double.parseDouble(str);
    // 执行其他操作
} catch (NumberFormatException e) {
    // 处理异常情况，例如输出错误信息或给予默认值
    System.out.println("无法解析字符串为数字");
}

1. Before parsing the string, you can first use a regular expression or other method to validate if the string is in a valid number format. For example:

if (str.matches("\\d+")) {
    // 字符串为合法的数字格式，可以进行解析
    double number = Double.parseDouble(str);
    // 执行其他操作
} else {
    // 字符串不是合法的数字格式，处理异常情况
    System.out.println("字符串格式不正确");
}

1. Utilize a subclass of the NumberFormat class (such as DecimalFormat) for formatting and parsing operations, and utilize its provided methods for handling exceptions. For example:

DecimalFormat decimalFormat = new DecimalFormat("#.##");
try {
    // 尝试解析字符串为数字
    double number = decimalFormat.parse(str).doubleValue();
    // 执行其他操作
} catch (ParseException e) {
    // 处理异常情况，例如输出错误信息或给予默认值
    System.out.println("无法解析字符串为数字");
}

These methods can assist you in resolving the NumberFormat exception. The selection of specific methods depends on your needs and code structure.