Java开发笔记（三十六）字符串的常用方法

		String hello = \"Hello World. \";
		// isEmpty方法判断该字符串是否为空串
		boolean isEmpty = hello.isEmpty();
		System.out.println(\"isEmpty = \"+isEmpty);
		// equals方法判断该字符串是否与目标串相等
		boolean equals = hello.equals(\"你好\");
		System.out.println(\"equals = \"+equals);
		// startsWith方法判断该字符串是否以目标串开头
		boolean startsWith = hello.startsWith(\"Hello\");
		System.out.println(\"startsWith = \"+startsWith);
		// endsWith方法判断该字符串是否以目标串结尾
		boolean endsWith = hello.endsWith(\"World\");
		System.out.println(\"endsWith = \"+endsWith);
		// contains方法判断该字符串是否包含了目标串
		boolean contains = hello.contains(\"or\");
		System.out.println(\"contains = \"+contains);

isEmpty = false
equals = false
startsWith = true
endsWith = false
contains = true

		String hello = \"Hello World. \";
		// length方法返回该字符串的长度
		int length = hello.length();
		System.out.println(\"length = \"+length);
		// charAt方法返回该字符串在指定位置的字符
		char first = hello.charAt(0);
		System.out.println(\"first = \"+first);
		// indexOf方法返回目标串在该字符串中第一次找到的位置
		int index = hello.indexOf(\"l\");
		System.out.println(\"index = \"+index);
		// lastIndexOf方法返回目标串在该字符串中最后一次找到的位置
		int lastIndex = hello.lastIndexOf(\"l\");
		System.out.println(\"lastIndex = \"+lastIndex);

length = 13
first = H
index = 2
lastIndex = 9

		String hello = \"Hello World. \";
		// toLowerCase方法返回转换为小写字母的字符串
		String lowerCase = hello.toLowerCase();
		System.out.println(\"lowerCase = \"+lowerCase);
		// toUpperCase方法返回转换为大写字母的字符串
		String upperCase = hello.toUpperCase();
		System.out.println(\"upperCase = \"+upperCase);
		// trim方法返回去掉首尾空格后的字符串
		String trim = hello.trim();
		System.out.println(\"trim = \"+trim);
		// concat方法返回在末尾添加了目标串之后的字符串
		String concat = hello.concat(\"Fine, thank you.\");
		System.out.println(\"concat = \"+concat);
		// substring方法返回从指定位置开始截取的子串。只有一个输入参数的substring，从指定位置一直截取到源串的末尾
		String subToEnd = hello.substring(6);
		System.out.println(\"subToEnd = \"+subToEnd);
		// 有两个输入参数的substring方法，返回从开始位置到结束位置中间截取的子串
		String subToCustom = hello.substring(6, 9);
		System.out.println(\"subToCustom = \"+subToCustom);
		// replace方法返回目标串替换后的字符串
		String replace = hello.replace(\"l\", \"L\");
		System.out.println(\"replace = \"+replace);

lowerCase = hello world. 
upperCase = HELLO WORLD. 
trim = Hello World.
concat = Hello World. Fine, thank you.
subToEnd = World. 
subToCustom = Wor
replace = HeLLo WorLd.