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package day04;
public class StringDemo2 {
public static void main(String[] args) {
String w1 = "a";
String w2 = w1.replaceAll("\\d?","t");
String w3 = "7";
String w4 = w3.replaceAll("\\d?","t");
System.out.println(w2);
System.out.println(w4);
}
}
String w3 = "71";
String w4 = w3.replaceAll("7{0}","t");
t7t1t
String w3 = "71";
String w4 = w3.replaceAll("7{0,1}","t");
tt1t 少个t是因为7{0,1}会匹配1{0}7 String w1 = "aaa";
String w2 = w1.replaceAll("\\d?","t");
tatatat
?其实就是{0,},“空”也会被匹配上,比如两个a之间的“空”。