java中String的操作api 收藏，stringapi

java中String的操作api 收藏，stringapi

创建一个字符串实例变量 StringBuffer buf = new StringBuffer("Java" ); // Append buf.append(" Almanac v1/" ); // Java Almanac v1/ buf.append(3 ); // Java Almanac v1/3 // Set int index = 15 ; buf.setCharAt(index, '.' ); // Java Almanac v1.3 // Insert index = 5 ; buf.insert(index, "Developers " );// Java Developers Almanac v1.3 // Replace int start = 27 ; int end = 28 ; buf.replace(start, end, "4" ); // Java Developers Almanac v1.4 // Delete start = 24 ; end = 25 ; buf.delete(start, end); // Java Developers Almanac 1.4 // Convert to string String s = buf.toString(); 比较字符串 String s1 = "a" ; String s2 = "A" ; String s3 = "B" ; // Check if identical 监测是否一致 boolean b = s1.equals(s2); // false // Check if identical ignoring case b = s1.equalsIgnoreCase(s2); // true // Check order of two strings 监测两个字符串的顺序 int i = s1.compareTo(s2); // 32; lowercase follows uppercase if (i < 0) { // s1 precedes s2 } else if (i > 0) { // s1 follows s2 } else { // s1 equals s2 } // Check order of two strings ignoring case i = s1.compareToIgnoreCase(s3); // -1 if (i < 0) { // s1 precedes s3 } else if (i > 0) { // s1 follows s3 } else { // s1 equals s3 } // A string can also be compared with a StringBuffer; StringBuffer sbuf = new StringBuffer("a"); b = s1.contentEquals(sbuf); // true 判断一个字符串中是否包含另外一个字符串 String string = "Madam, I am Adam" ; // Starts with boolean b = string.startsWith("Mad" ); // true // Ends with b = string.endsWith("dam" ); // true // Anywhere b = string.indexOf("I am" ) > 0; // true // To ignore case, regular expressions must be used // Starts with b = string.matches("(?i)mad.*" ); // Ends with b = string.matches("(?i).*adam" ); // Anywhere b = string.matches("(?i).*i am.*" ); 获取制定字符串中的子串 int start = 1 ; int end = 4 ; String substr = "aString" .substring(start, end); // Str 查询指定字符串中的子串以及字母的位置 String string = "madam, i am Adam" ; // Characters // First occurrence of a c int index = string.indexOf('a' ); // 1 // Last occurrence index = string.lastIndexOf('a' ); // 14 // Not found index = string.lastIndexOf('z' ); // -1 // Substrings // First occurrence index = string.indexOf("dam" ); // 1 // Last occurrence index = string.lastIndexOf("dam" ); // 13 // Not found index = string.lastIndexOf("z" ); // -1 取代制定字符的函数操作 // Replace all occurrences of 'a' with 'o' String newString = string .replace('a' , 'o' ); 取代制定字符串的操作 static String replace(String str, String pattern, String replace) { int s = 0; int e = 0; StringBuffer result = new StringBuffer(); while ((e = str.indexOf(pattern, s)) >= 0) { result.append(str.substring(s, e)); result.append(replace); s = e+pattern.length(); } result.append(str.substring(s)); return result.toString(); } 转变字符串的大小写 // Convert to upper case String upper = string .toUpperCase(); // Convert to lower case String lower = string .toLowerCase(); Converting a Primitive Type Value to a String // Use String.valueOf() String s = String.valueOf(true ); // true s = String.valueOf((byte)0x12 ); // 18 s = String.valueOf((byte)0xFF ); // -1 s = String.valueOf('a' ); // a s = String.valueOf((short)123 ); // 123 s = String.valueOf(123 ); // 123 s = String.valueOf(123L ); // 123 s = String.valueOf(1.23F ); // 1.23 s = String.valueOf(1.23D ); // 1.23 // Use + s = ""+true ; // true s = ""+((byte)0x12 ); // 18 s = ""+((byte)0xFF ); // -1 s = ""+'a' ; // a s = ""+((short)123 ); // 123 s = ""+123 ; // 123 s = ""+123L ; // 123 s = ""+1.23F ; // 1.23 s = ""+1.23D ; // 1.23 Converting Between Unicode and UTF-8 try { // Convert from Unicode to UTF-8 String string = "abc/u5639/u563b" ; byte[] utf8 = string.getBytes("UTF-8"); // Convert from UTF-8 to Unicode string = new String(utf8, "UTF-8"); } catch (UnsupportedEncodingException e) { } Determining a Character's Unicode Block char ch = '/u5639' ; Character.UnicodeBlock block = Character.UnicodeBlock.of(ch); Determining If a String Is a Legal Java Identifier // Returns true if s is a legal Java identifier. public static boolean isJavaIdentifier(String s) { if (s.length() == 0 || !Character.isJavaIdentifierStart(s.charAt(0))) { return false; } for (int i=1; i