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public static boolean isNum(String str) {
return str.matches("^[-+]?(([0-9]+)([.]([0-9]+))?|([.]([0-9]+))?)$");
}
public class A {
public static void main(String[] args) {
System.out.println(isNum(""));
System.out.println(isNum("1"));
System.out.println(isNum("1.1"));
System.out.println(isNum("1."));
System.out.println(isNum(".1"));
System.out.println(isNum("0.1"));
System.out.println(isNum("a"));
}
public static boolean isNum(String str) {
return str.matches("^[-+]?((([0-9]+)([.]([0-9]+))?)|([.]([0-9]+)))$");
}
}
[+-]*?\d+\.*?\d+
[+-]*?\d+\.\d+
这个表达式可以么?