Java 如何检查字符串是否为有效整数？
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How to check if a string is a valid integer?
提问by Dannyl
I have:
我有：
op1 = Integer.parseInt(jTextField1.getText());
op2 = Integer.parseInt(jTextField2.getText());
However, I want to check first whether the text fields' values can be assigned to integer variables. How do I do that?
但是，我想首先检查文本字段的值是否可以分配给整数变量。我怎么做？
I've been going through this for a long time, so, if this was already asked here, forgive me
我已经经历了很长时间，所以，如果这里已经问过这个问题，请原谅我
采纳答案by Warlord
You can't do if (int i = 0), because assignment returns the assigned value (in this case 0) and ifexpects an expression that evaluates either to true, or false.
您不能这样做if (int i = 0)，因为赋值返回分配的值（在本例中为0）并if期望计算结果为true或的表达式false。
On the other hand, if your goal is to check, whether jTextField.getText()returns a numeric value, that can be parsed to int, you can attempt to do the parsing and if the value is not suitable, NumberFormatExceptionwill be raised, to let you know.
另一方面，如果您的目标是检查是否jTextField.getText()返回一个可以解析为的数值int，您可以尝试进行解析，如果该值不合适，NumberFormatException将被提出，让您知道。
try {
op1 = Integer.parseInt(jTextField1.getText());
} catch (NumberFormatException e) {
System.out.println("Wrong number");
op1 = 0;
}
回答by Smutje
Basically, you have to decide to check if a given string is a valid integer or you simply assume a given string is a valid integer and an exception can occur at parsing.
基本上，您必须决定检查给定字符串是否是有效整数，或者您只是假设给定字符串是有效整数，并且在解析时可能会发生异常。
回答by xp500
parseInt throws NumberFormatException if it cannot convert the String to an int. So you should surround the parseInt calls with a try catch block and catch that exception.
如果 parseInt 无法将 String 转换为 int，则会抛出 NumberFormatException。所以你应该用 try catch 块包围 parseInt 调用并捕获该异常。
回答by Niroshan Abeywickrama
This works for me. Simply to identify whether a String is a primitive or a number.
这对我有用。简单地识别一个字符串是原始值还是数字。
private boolean isPrimitive(String value){
boolean status=true;
if(value.length()<1)
return false;
for(int i = 0;i<value.length();i++){
char c=value.charAt(i);
if(Character.isDigit(c) || c=='.'){
}else{
status=false;
break;
}
}
return status;
}