英文:
Java Regex to extract a number from a String
问题
我有以下的字符串输入。
String s = "我有5000个香蕉";
我正在使用正则表达式提取数字值 String regex = "\\b\\d+\\b"。这个正则表达式很好，因为它会排除任何数字和字母混合的词，比如 a4 bc3。
问题出在当用户输入类似以下的字符串时：
String s1 = "我有2 345个香蕉";
String s2 = "我有2,345个香蕉";
String s3 = "我有#2345个香蕉";
String s4 = "我有5654 6个香蕉";
我的程序应该对上述情况输出空字符串，因为输入字符串中没有有效的数字。
英文:
I have the following String input.
String s = "I have 5000 bananas";
I am extracting the numeric value using a regex String regex = "\\b\\d+\\b". This Regex is good in the sense that it would exclude any numericalAlpha mix words like a4 bc3.
The issue happens when the user will input Strings like
String s1 = "I have 2 345 bananas";
String s2 = "I have 2,345 bananas";
String s3 = "I have #2345 bananas";
String s4 = "I have 5654 6 bananas";
My program should output an empty string in the above cases as none are valid numbers in the input String.
答案1
得分: 0
你想要使用一个capturing group和String方法replaceAll。
String[] strs = new String[] {
"我有 5000 个香蕉",
"我有 2 345 个香蕉",
"我有 2,345 个香蕉",
"我有 #2345 个香蕉",
"我有 5654 6 个香蕉"
};
for (String s : strs) {
if (s.matches("(\\d+)( \\D+)")) {
System.out.println(s.replaceAll("(\\d+)( \\D+)", "$1"));
}
else if (s.matches("(\\D+ )(\\d+)")) {
System.out.println(s.replaceAll("(\\D+ )(\\d+)", "$2"));
}
else if (s.matches("(\\D+ )(\\d+)( \\D+)")) {
System.out.println(s.replaceAll("(\\D+ )(\\d+)( \\D+)", "$2"));
}
else {
// 仅用于演示“显示”或
// 如果需要返回或分配空字符串
System.out.println("");
}
}
使用您提供的测试案例运行将产生：（我使用字符串"No match"代替空字符串只是为了演示）
5000
No match
No match
No match
No match
英文:
You want to use a capturing group and the String method replaceAll.
...
String[] strs = new String[] {
"I have 5000 bananas",
"I have 2 345 bananas",
"I have 2,345 bananas",
"I have #2345 bananas",
"I have 5654 6 bananas"
};
for (String s : strs) {
if (s.matches("(\\d+)( \\D+)")) {
System.out.println(s.replaceAll("(\\d+)( \\D+)", "$1"));
}
else if (s.matches("(\\D+ )(\\d+)")) {
System.out.println(s.replaceAll("(\\D+ )(\\d+)", "$2"));
}
else if (s.matches("(\\D+ )(\\d+)( \\D+)")) {
System.out.println(s.replaceAll("(\\D+ )(\\d+)( \\D+)", "$2"));
}
else {
// Just for demonstration on "displaying" or
// if you need to return or assign an empty string
System.out.println("");
}
}
...
Running that for your provided test cases will yield: (I am using the string "No match" instead of an empty string just to demonstrate)
5000
No match
No match
No match
No match
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