数量词

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数量词

Greedy 数量词
X?的含义：
X，一次或一次也没有

X*的含义：
X，零次或多次

X+的含义：
X，一次或多次

X{n}的含义：
X，恰好 n 次

X{n,}的含义：
X，至少 n 次

X{n,m}的含义：
X，至少 n 次，但是不超过 m 次

package com.heima.regex;
public class Demo04_Regex {
	public static void main(String[] args) {
		//demo1();
		//demo2();
		//demo3();
		//demo4();
		//demo5();
		String regex = "[abc]{5,15}";
		System.out.println("abcba".matches(regex));
		System.out.println("abcbaabcabbabab".matches(regex));
		System.out.println("abcb".matches(regex));
		System.out.println("abcbaabaabcbaaba".matches(regex));
	}

	public static void demo5() {
		String regex = "[abc]{5,}";
		System.out.println("abcba".matches(regex));
		System.out.println("abcbaabcabbabab".matches(regex));
		System.out.println("abcb".matches(regex));
		System.out.println("abcbaaba".matches(regex));
	}

	public static void demo4() {
		String regex = "[abc]{5}";
		System.out.println("abcba".matches(regex));
		System.out.println("abcbaabcabbabab".matches(regex));
		System.out.println("abcb".matches(regex));
		System.out.println("abcbaaba".matches(regex));
	}

	public static void demo3() {
		String regex = "[abc]+";
		System.out.println("".matches(regex));
		System.out.println("a".matches(regex));
		System.out.println("aaaaabbbbccccc".matches(regex));
	}

	public static void demo2() {
		String regex = "[abc]*";
		System.out.println("".matches(regex));
		System.out.println("abc".matches(regex));
		System.out.println("a".matches(regex));
	}

	public static void demo1() {
		String regex = "[abc]?";
		System.out.println("a".matches(regex));
		System.out.println("b".matches(regex));
		System.out.println("c".matches(regex));
		System.out.println("d".matches(regex));
		System.out.println("".matches(regex));
	}
}