【Java】String

public class StringDemo {private static final long LEVEL = 20150701;//码讲版本/* * String 基本操作 */@Testpublic void stringtest1() throws UnsupportedEncodingException {String s1 = "123abc";String s2 = "123abc";String s3 = "123";String s4 = s3 + "abc";String s5 = "123" + "abc";String s6 = 1 + "23" + "abc";String s7 = 1 + '2' + "3abc";String s8 = new String("123abc");System.out.println(s1 == s2);// true String直接量会使用缓存System.out.println(s1 == s4);// false 只要有变量参与就新建对象存System.out.println(s1 == s5);// true 编译器会将直接量计算后在运行System.out.println(s1 == s6);// trueSystem.out.println(s1 == s7);// false 1+‘2’将为数字System.out.println(s1 == s8);// falseSystem.out.println(s1.equals(s8));// trueSystem.out.println("length：" + s1.length());// java字母和汉字占的字节数与才用的编码方式有关System.out.println("j".getBytes("UTF-8").length);// 1System.out.println("好".getBytes("UTF-8").length);// 3}/* * indexOf lastIndesOf */public void stringTest3() {String str = "thinking in java";int index = str.indexOf("java");int index1 = str.indexOf("in", 3);int index2 = str.lastIndexOf("in");System.out.println(index + "overload" + index1 + "last" + index2);// 12overload5last9}// 找出所有字串的位置public void findStr() {String str = "**java***java*****java*";String str1 = "java";int index = 0;while ((index = str.indexOf(str1, index)) != -1) {System.out.print(index + "");index += str1.length();// 减少查找，提高速度}}/* * substring */public void stringTest4() {String str = "thinking in java";System.out.println(str.substring(4, 8));// kingSystem.out.println(str.substring(9));// in java}public void stringTest5() {String url = "http://www.baidu.com";int start = url.indexOf(".") + 1;int end = url.indexOf(".", start);// int end = url.lastIndexOf(".");String str = url.substring(start, end);System.out.println(str);}/* * trim */public void stringTest6() {String str = " \t lksjelk" + "\n";System.out.println(str);System.out.println(str.trim());}/* * charAt */public void testCharAt() {String str = "Thinking in Java";System.out.println(str.charAt(6));}/* * startWith  endsWith */public void testStart() {String str = "Thinking in Java";System.out.println(str.startsWith("Thi"));// trueSystem.out.println(str.endsWith("va"));// true}/* * toLowerCase   toUpperCase */public void testLowerAndUpper() {String str = "jslfjAFFKDJ";System.out.println(str.toLowerCase());System.out.println(str.toUpperCase());}/* * valueOf */// @Testpublic void testValueOf() {// if .class will return class nameString str = String.valueOf(new TestToString());//TestToString在最后面System.out.println(str);}/* * 判断一个字符串是否为回文 */public void isHuiwen() {String str = "上海自来水来自海上";for (int i = 0; i < str.length() / 2; i++) {if (str.charAt(i) != str.charAt(str.length() - 1 - i)) {System.out.println("是回文");return;}}System.out.println("不是回文");}/* * 输出所有汉字 */public void printCh() {StringBuilder builder = new StringBuilder();for (char i = '\u4e00', sum = 1; i <= '\u9fa5'; i++, sum++) {builder.append(i);if (sum % 50 == 0) {builder.append("\n");}}System.out.println(builder.toString());}// ++++++++++++++++++++++++==正则表达式+++++++++++++++++++=/* * match */public void testMatch() {// 匹配email java默认进行全匹配String regex = "\\w+@\\w+(\\.[a-zA-Z]+)+";String email = "[e-mail]";if (email.matches(regex)) {System.out.println("This is a email!");} else {System.out.println("This can't be a email");}}/** * split图片重命名 */public void testSplit() {// ,,,123,123,,,123,,,-->[, , , 123, 123, , , , 43, 545, 435]String regex = "\\.";String str = "123.jpg";String[] strs = str.split(regex);str = System.currentTimeMillis() + "." + strs[1];System.out.println(str);}/** * replaceAll用于和谐聊天用语 */public void testReplaceAll() {String str = "skj234glskej34234jlj3lk4234lkj2l3kj4lk3";str = str.replaceAll("\\d+", "#");System.out.println(str);}/* * StringBuilder  replace  delete  insert  reverse */public void testStringBuilder() {StringBuilder sb = new StringBuilder("this is a test string");System.out.println("原始字符：" + sb);sb.replace(15, sb.length(), "StringBuilder");System.out.println("replace后字符：" + sb.toString());sb.delete(0, 4);System.out.println("delete后字符：" + sb.toString());sb.insert(0, "that");System.out.println("insert后字符：" + sb.toString());sb.reverse();System.out.println("reverse后字符：" + sb.toString());}}class TestToString {@Overridepublic String toString() {return "toString called";}}