Java(TM) Boutique - Java Books - Java in a Nutshell, 4th Edition

// Creating strings String s = "Now"; // String objects have a special literal syntax String t = s + " is the time."; // Concatenate strings with + operator String t1 = s + " " + 23.4; // + converts other values to strings t1 = String.valueOf('c'); // Get string corresponding to char value t1 = String.valueOf(42); // Get string version of integer or any value t1 = object.toString(); // Convert objects to strings with toString() // String length int len = t.length(); // Number of characters in the string: 16 // Substrings of a string String sub = t.substring(4); // Returns char 4 to end: "is the time." sub = t.substring(4, 6); // Returns chars 4 and 5: "is" sub = t.substring(0, 3); // Returns chars 0 through 2: "Now" sub = t.substring(x, y); // Returns chars between pos x and y-1 int numchars = sub.length(); // Length of substring is always (y-x) // Extracting characters from a string char c = t.charAt(2); // Get the 3rd character of t: w char[] ca = t.toCharArray(); // Convert string to an array of characters t.getChars(0, 3, ca, 1); // Put 1st 3 chars of t into ca[1]-ca[3] // Case conversion String caps = t.toUpperCase(); // Convert to uppercase String lower = t.toLowerCase(); // Convert to lowercase // Comparing strings boolean b1 = t.equals("hello"); // Returns false: strings not equal boolean b2 = t.equalsIgnoreCase(caps); // Case-insensitive compare: true boolean b3 = t.startsWith("Now"); // Returns true boolean b4 = t.endsWith("time."); // Returns true int r1 = s.compareTo("Pow"); // Returns < 0: s comes before "Pow" int r2 = s.compareTo("Now"); // Returns 0: strings are equal int r3 = s.compareTo("Mow"); // Returns > 0: s comes after "Mow" r1 = s.compareToIgnoreCase("pow"); // Returns < 0 (Java 1.2 and later) // Searching for characters and substrings int pos = t.indexOf('i'); // Position of first 'i': 4 pos = t.indexOf('i', pos+1); // Position of the next 'i': 12 pos = t.indexOf('i', pos+1); // No more 'i's in string, returns -1 pos = t.lastIndexOf('i'); // Position of last 'i' in string: 12 pos = t.lastIndexOf('i', pos-1); // Search backwards for 'i' from char 11 pos = t.indexOf("is"); // Search for substring: returns 4 pos = t.indexOf("is", pos+1); // Only appears once: returns -1 pos = t.lastIndexOf("the "); // Search backwards for a string String noun = t.substring(pos+4); // Extract word following "the" // Replace all instances of one character with another character String exclaim = t.replace('.', '!'); // Works only with chars, not substrings // Strip blank space off the beginning and end of a string String noextraspaces = t.trim(); // Obtain unique instances of strings with intern() String s1 = s.intern(); // Returns s1 equal to s String s2 = "Now".intern(); // Returns s2 equal to "Now" boolean equals = (s1 == s2); // Now can test for equality with ==

char[] text; // An array of characters, initialized somewhere else int p = 0; // Our current position in the array of characters // Skip leading whitespace while((p < text.length) && Character.isWhitespace(text[p])) p++; // Capitalize the first word of text while((p < text.length) && Character.isLetter(text[p])) { text[p] = Character.toUpperCase(text[p]); p++; }

// Create a string buffer from a string StringBuffer b = new StringBuffer("Mow"); // Get and set individual characters of the StringBuffer char c = b.charAt(0); // Returns 'M': just like String.charAt() b.setCharAt(0, 'N'); // b holds "Now": can't do that with a String! // Append to a StringBuffer b.append(' '); // Append a character b.append("is the time."); // Append a string b.append(23); // Append an integer or any other value // Insert Strings or other values into a StringBuffer b.insert(6, "n't"); // b now holds: "Now isn't the time.23" // Replace a range of characters with a string (Java 1.2 and later) b.replace(4, 9, "is"); // Back to "Now is the time.23" // Delete characters b.delete(16, 18); // Delete a range: "Now is the time" b.deleteCharAt(2); // Delete 2nd character: "No is the time" b.setLength(5); // Truncate by setting the length: "No is" // Other useful operations b.reverse(); // Reverse characters: "si oN" String s = b.toString(); // Convert back to an immutable string s = b.substring(1,2); // Or take a substring: "i" b.setLength(0); // Erase buffer; now it is ready for reuse

/** * Return a prefix of the specified CharSequence that starts at the first * character of the sequence and extends up to (and includes) the first * occurrence of the character c in the sequence. Returns null if c is * not found. s may be a String, StringBuffer, or java.nio.CharBuffer. */ public static CharSequence prefix(CharSequence s, char c) { int numChars = s.length(); // How long is the sequence? for(int i = 0; i < numChars; i++) { // Loop through characters in sequence if (s.charAt(i) == c) // If we find c, return s.subSequence(0,i+1); // then return the prefix subsequence } return null; // Otherwise, return null }