Java學習日誌14.1(第一階段基礎)
阿新 • • 發佈:2018-11-03
**2018.10.20 陰
黑馬程式設計師養成記錄第一天
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正則表示式:*
*定義:一個用來描述或者匹配一系列符合某個語法規則的字串的單個字串。
*作用:比如註冊郵箱,郵箱有使用者名稱和密碼,一般會對其限制長度,這個長度的事情就是正則表示式做的。
1.常見物件-(字元類)
字元類
*[abc] a,b,或c(簡單類)
*[^abc] 任意字元,除了a,b或c(否定)
*[a-z A-Z] a到z或A到Z,兩頭的字母包括在內(範圍)
*[0-9] 0到9的字元都包括
實現程式碼
package com.heima.Regex; public class demo2T_Regex { public static void main(String[] args) { demo1(); System.out.println("----------"); demo2(); System.out.println("----------"); demo3(); System.out.println("----------"); demo4(); } private static void demo4() { String regex = "[0-9]"; System.out.println("1".matches(regex)); System.out.println("0".matches(regex)); System.out.println("d".matches(regex)); System.out.println("9".matches(regex)); } private static void demo3() { String regex = "[a-zA-Z]"; System.out.println("a".matches(regex)); System.out.println("z".matches(regex)); System.out.println("A".matches(regex)); System.out.println("1".matches(regex)); } private static void demo2() { String regex = "[^abc]"; System.out.println("a".matches(regex)); System.out.println("b".matches(regex)); System.out.println("d".matches(regex)); System.out.println("1".matches(regex)); } private static void demo1() { String regex = "[abc]"; System.out.println("a".matches(regex)); System.out.println("b".matches(regex)); System.out.println("d".matches(regex)); System.out.println("10".matches(regex)); } } } private static void demo2() { String regex = "[^abc]"; System.out.println("a".matches(regex)); System.out.println("b".matches(regex)); System.out.println("d".matches(regex)); System.out.println("1".matches(regex)); } private static void demo1() { String regex = "[abc]"; System.out.println("a".matches(regex)); System.out.println("b".matches(regex)); System.out.println("d".matches(regex)); System.out.println("10".matches(regex)); } } 程式結果: true true false false ---------- false false true true ---------- true true true false ---------- true true false true
2,常見物件(預定義字元)
A:預定義字元類
* . 任何字元。
* \d 數字:[0-9]
* \D 非數字 [^0-9]
* \s 空白字元[\t\n\r\x0B\f]
* \S 非空白字元 [^\s]
* \w 單詞字元:[a-zA-Z_0-9]
* \W 非單詞字元:[^\w]
實現程式碼:
package com.heima.Regex; public class regex3_Regex { public static void main(String[] args) { demo1(); System.out.println("----------"); demo2(); System.out.println("----------"); demo3(); System.out.println("----------"); demo4(); System.out.println("----------"); demo5(); System.out.println("----------"); demo6(); System.out.println("----------"); demo7(); System.out.println("----------"); demo8(); } private static void demo8() { String regex = "\\W"; System.out.println("a".matches(regex)); //false System.out.println("Z".matches(regex)); //false System.out.println("_".matches(regex)); //false System.out.println("0".matches(regex)); //false System.out.println("%".matches(regex)); //true } private static void demo7() { String regex = "\\w"; System.out.println("a".matches(regex)); //true System.out.println("Z".matches(regex)); //true System.out.println("_".matches(regex)); //true System.out.println("0".matches(regex)); //true System.out.println("%".matches(regex)); //false } private static void demo6() { String regex = "\\S"; System.out.println(" ".matches(regex)); //false System.out.println(" ".matches(regex));//table//false System.out.println("a".matches(regex)); //true } private static void demo5() { String regex = "\\s"; System.out.println(" ".matches(regex));//單空格 //true System.out.println(" ".matches(regex));//tab鍵 //true System.out.println(" ".matches(regex));//四個空格 //false } private static void demo4() { String regex = "\\D"; System.out.println("9".matches(regex)); //false System.out.println("0".matches(regex)); //false System.out.println("a".matches(regex)); //true } private static void demo3() { String regex = "\\d"; System.out.println("9".matches(regex)); //true System.out.println("0".matches(regex)); //true System.out.println("a".matches(regex)); //false } private static void demo2() { demo3(); } private static void demo1() { String regex = "."; //一個點代表一個字元 System.out.println("a".matches(regex)); //true System.out.println("ab".matches(regex)); //false } } 程式結果: true false ---------- true true false ---------- true true false ---------- false false true ---------- true true false ---------- false false true ---------- true true true true false ---------- false false false false true