String类常用方法总结

一时失言乱红尘 2022-07-28 04:16 235阅读 0赞

/**
     * 关于String类的常用方法总结
     * @author lsq
     *
     */
    public class StringAPIDemo {
    	
    	public static void main(String[] args) {
    	
    		/*
    		 * public char[] toCharArray()将一个字符串变成字符数组
    		 * public byte[] getBytes()将一个字符串变成字节数组
    		 */
    		String str = "Hello";
    		char[] charArray = str.toCharArray();
    		byte[] bytes = str.getBytes();
    		//循环输出字符数组
    		for (int i = 0; i < charArray.length; i++) {
    			System.out.print(charArray[i]+",");
    		}
    		//循环输出字节数组
    		for (int i = 0; i < bytes.length; i++) {
    			System.out.print(bytes[i]+",");
    		}
    		System.out.println("");
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    
    		/*
    		 * public String(char[] value)将字符数组变成一个字符串
    		 * public String(char[] value, int offset, int count)将制定范围内的字符变为字符串，offset是起始点，count是长度
    		 * public String(byte[] bytes)将全部的字节数组变成字符串
    		 * public String(byte[] bytes, int offset, int length)将制定范围内的字节数组变成字符串，offset是起始点，count是长度
    		 */
    		char charArray2[] = {'H','E','L','L','O',' ','J','A','V','A'};
    		byte bytes2[] = {'1','2','3','4'};
    		String char2str1 = new String(charArray2);
    		String char2str2 = new String(charArray2, 3, 2);
    		String byte2str1 = new String(bytes2);
    		String byte2str2 = new String(bytes2, 1, 2);
    		System.out.println("char2str1的值是："+char2str1);
    		System.out.println("char2str2的值是："+char2str2);
    		System.out.println("byte2str1的值是："+byte2str1);
    		System.out.println("byte2str2的值是："+byte2str2);
    		System.out.println("");
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * public char charAt(int index)从一个字符串中取出指定位置的字符
    		 */
    		String charAtTest = "charAtTest";
    		char c = charAtTest.charAt(4);
    		System.out.println("charAtTest位置为4的字符是："+c);
    		System.out.println("");
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    
    		/*
    		 * public int length()获取字符串的长度
    		 */
    		String strLength = "strLength";
    		int length = strLength.length();
    		System.out.println(length);
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * 查找指定的字符串是否存在：
    		 * public int indexOf(String str)从头开始查找字符串是否存在，返回int类型，若查找不到，返回-1
    		 * public int indexOf(String str, int fromIndex)从指定位置开始查找指定的字符串是否存在，返回int类型，找不到返回-1
    		 */
    		
    		String strindexOf = "abcdefgcdhi";
    		System.out.println(strindexOf.indexOf("cd"));
    		System.out.println(strindexOf.indexOf("c",3));
    		System.out.println(strindexOf.indexOf("j"));
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * public String trim()去掉字符串中左右的空格，但中间的空格不会去掉
    		 */
    		
    		String strTrim = " Hello java ";
    		System.out.println(strTrim.trim());
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		
    		/*
    		 * 字符串截取：从一个字符串中取出部分内容
    		 * substring(int beginIndex)从指定位置开始截取至字符串结尾、
    		 * subString(int beginIndex, int endIndex)截取指定范围的字符串，不包括结束位置的字符（☆）
    		 */
    		String strsubString = "i love java!";
    		System.out.println(strsubString.substring(2));
    		System.out.println(strsubString.substring(2,8));
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * public String[] split(String regex)拆分字符串，以某一个字符串作为拆分点
    		 */
    		String strsplit = "Hello World! How are you?";
    		String[] splits = strsplit.split(" ");
    		for (int i = 0; i < splits.length; i++) {
    			System.out.println(splits[i]);
    		}
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * public String toLowerCase():将字符串字符都变为小写
    		 * public String toUpperCase():将字符串字符都变为大写
    		 */
    		String strToCase = "Hello java!";
    		System.out.println(strToCase.toLowerCase());
    		System.out.println(strToCase.toUpperCase());
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * 判断是否以指定的字符串开头或者结尾
    		 * public boolean startsWith(String prefix):判断是否以指定的字符串开头
    		 * public boolean endsWith(String suffix):判断是否以指定的字符串结尾
    		 */
    		String strWith = "Hello World!";
    		boolean s = strWith.startsWith("Hel");
    		System.out.println(s);
    		boolean e = strWith.endsWith("d!");
    		System.out.println(e);
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    
    		/*
    		 * 判断两个字符串是否相等：
    		 * public boolean equals(Object anObject):区分大小写
    		 * public boolean equalsIgnoreCase(String anotherString):不区分大小写
    		 */
    		String strEquals1 = "String";
    		String strEquals2 = "string";
    		System.out.println(strEquals1.equals(strEquals2));
    		System.out.println(strEquals1.equalsIgnoreCase(strEquals2));
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    		/*
    		 * 字符串替换功能
    		 * public String replace(CharSequence target, CharSequence replacement)
    		 * public String replaceAll(String regex, String replacement):将指定的字符regex替换成指定的replacement
    		 */
    		String strReplace = "Hello java!";
    		System.out.println(strReplace.replace('o', 'l'));
    		System.out.println(strReplace.replaceAll("java", "World"));
    		System.out.println("~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~");
    		
    	}
    }