【Java】String

public class StringDemo {
	private static final long LEVEL = 20150701;//码讲版本
	/*
	 * String 基本操作
	 */
	@Test
	public 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);// true
		System.out.println(s1 == s7);// false 1+‘2’将为数字
		System.out.println(s1 == s8);// false
		System.out.println(s1.equals(s8));// true
		System.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);// 1
		System.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));// king
		System.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"));// true
		System.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
	 */
	// @Test
	public void testValueOf() {
		// if .class will return class name
		String 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 = "fancq@slkjfl.com.cn";
		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 {
	@Override
	public String toString() {
		return "toString called";
	}
}