public static final int UNIX_LINES = 0x01;/*** 启用不区分大小写的匹配。*/public static final int CASE_INSENSITIVE = 0x02;/*** 模式中允许空白和注释。*/public static final int COMMENTS = 0x04;/*** 启用多行模式。*/public static final int MULTILINE = 0x08;/*** 启用模式的字面值解析。*/public static final int LITERAL = 0x10;/*** 启用 dotall 模式。*/public static final int DOTALL = 0x20;/*** 启用 Unicode 感知的大小写折叠。*/public static final int UNICODE_CASE = 0x40;/***  启用规范等价。*/public static final int CANON_EQ = 0x80;private static final long serialVersionUID = 5073258162644648461L;/*** The original regular-expression pattern string.*/private String pattern;/*** The original pattern flags.*/private int flags;/*** Boolean indicating this Pattern is compiled; this is necessary in order* to lazily compile deserialized Patterns.*/private transient volatile boolean compiled = false;/*** The normalized pattern string.*/private transient String normalizedPattern;/*** The starting point of state machine for the find operation.  This allows* a match to start anywhere in the input.*/transient Node root;/*** The root of object tree for a match operation.  The pattern is matched* at the beginning.  This may include a find that uses BnM or a First* node.*/transient Node matchRoot;/*** Temporary storage used by parsing pattern slice.*/transient int[] buffer;/*** Temporary storage used while parsing group references.*/transient GroupHead[] groupNodes;/*** Temporary null terminated code point array used by pattern compiling.*/private transient int[] temp;/*** The number of capturing groups in this Pattern. Used by matchers to* allocate storage needed to perform a match.此模式中的捕获组的数目。*/transient int capturingGroupCount;/*** The local variable count used by parsing tree. Used by matchers to* allocate storage needed to perform a match.*/transient int localCount;/*** Index into the pattern string that keeps track of how much has been* parsed.*/private transient int cursor;/*** Holds the length of the pattern string.*/private transient int patternLength;

    private Pattern(String p, int f) {pattern = p;flags = f;// Reset group index countcapturingGroupCount = 1;localCount = 0;if (pattern.length() > 0) {compile();} else {root = new Start(lastAccept);matchRoot = lastAccept;}}

    public static Pattern compile(String regex) {return new Pattern(regex, 0);}

    public static Pattern compile(String regex, int flags) {return new Pattern(regex, flags);}

    public Matcher matcher(CharSequence input) {if (!compiled) {synchronized(this) {if (!compiled)compile();}}Matcher m = new Matcher(this, input);return m;}

    public static boolean matches(String regex, CharSequence input) {Pattern p = Pattern.compile(regex);Matcher m = p.matcher(input);return m.matches();}

        Pattern p = Pattern.compile("a*b");Matcher m = p.matcher("aaaaab");boolean b = m.matches();System.out.println(b);// true

        System.out.println(Pattern.matches("a*b", "aaaaab"));// true

    public String[] split(CharSequence input) {return split(input, 0);}

public static void main(String[] args) {String[] arr = null;CharSequence input = "boo:and:foo";Pattern p = Pattern.compile("o");arr = p.split(input, -2);System.out.println(printArr(arr));// {"b","",":and:f","",""}，共有5个元素arr = p.split(input, 2);System.out.println(printArr(arr));// {"b","o:and:foo"}，共有2个元素arr = p.split(input, 7);System.out.println(printArr(arr));// {"b","",":and:f","",""}，共有5个元素arr = p.split(input, 0);System.out.println(printArr(arr));// {"b","",":and:f"}，共有3个元素
    }// 打印String数组public static String printArr(String[] arr) {int length = arr.length;StringBuffer sb = new StringBuffer();sb.append("{");for (int i = 0; i < length; i++) {sb.append("\"").append(arr[i]).append("\"");if (i != length - 1)sb.append(",");}sb.append("}").append("，共有" + length + "个元素");return sb.toString();}

   public String toString() {return pattern;}

    public String pattern() {return pattern;}

Pattern p = Pattern.compile("\\d+");
System.out.println(p.toString());// 输出\d+
System.out.println(p.pattern());// 输出\d+

    public int flags() {return flags;}

Pattern p = Pattern.compile("a+", Pattern.CASE_INSENSITIVE);
System.out.println(p.flags());// 2

public static final int CASE_INSENSITIVE = 0x02;