@Test public void demo(){ // 以下为String中的常用的方法及注释， 最常用的注释前有**标注 String s = "abcdefg123456"; // 返回下标对应的ASCII码 int codePointAt = s.codePointAt(7); // **返回字符串s和字符串Q的，第一个不相等字符的ASCII码差值，如果查找结束发现都相等，则返回两个字符串的长度差值 int compareTo = s.compareTo("Q"); // 返回下标前一位对应的ASCII码 int codePointBefore = s.codePointBefore(7); // 返回代码点长度 int codePointCount = s.codePointCount(4, 7); // 返回从index=4处偏移到codePointOffSet=7之后的索引 int offsetByCodePoints = s.offsetByCodePoints(4, 7); // 将字符串变成字节数组 byte[] getBytes = s.getBytes(); // **将字符串变成字符数组 char[] toCharArray = s.toCharArray(); // **返回指定索引出的字符 char charAt = s.charAt(7); // **是否包含字符串"contains" boolean contains = s.contains("contains"); // **将字符串s中的c全部替换为C String replaceAll = s.replaceAll("c", "C"); // 将字符串中的1替换为一 String replace = s.replace("1", "一"); // **截取字符串s中的索引从0到3的字符 String substring = s.substring(0, 3); // 截取字符串s中索引从4开始的字符 String substring1 = s.substring(4); // 字符串s是否以6结尾 boolean endsWith = s.endsWith("6"); // 字符串是否以a开头 boolean startsWith = s.startsWith("compareTo"); // **将字符串s以字符c进行分割 String[] split = s.split("c"); // 将字符串s以字符c进行分割，分割成3份(如果最大能够分割到3份的话，如果最大不能分割到3份，则默认分割到最大份数) String[] split1 = s.split("c", 3); // 将字符串7890拼接到字符串s的后面，与+拼接字符串的区别是，+号左右的字符串都可以是null，而concat左右都不允许，否则会报空指针异常 String concat = s.concat("7890"); // 返回字符串是否相等，与equals区别，equals仅限于两个String类型字符串进行比较，而contentEquals可以比较类型为CharSequence的， // 而且如果比较的是StringBuffer还会加锁 boolean contentEquals = s.contentEquals("contentEquals"); // 比较两个字符串是否相等(忽略大小写)， boolean equalsIgnoreCase = s.equalsIgnoreCase("Abcdefg123456"); // **比较两个字符串是否相等(不忽略大小写) boolean equals = s.equals("contentEquals"); // 判断字符串是否为空 boolean empty = s.isEmpty(); // **获取字符串的长度 int length = s.length(); // **返回指定字符在字符串s中的索引，如果找不到返回-1 int indexOf = s.indexOf("一"); // 将字符串全部转换为小写 String toLowerCase = s.toLowerCase(); // 将字符串全部转换为大写 String toUpperCase = s.toUpperCase(); // 去除字符串前后的空格 String trim = " abc ".trim(); // 将指定数量的字符串(s,7890,AAA)以固定格式(,)进行拼接 String join = String.join(",",s, "7890", "AAA"); System.out.println("codePointAt = " + codePointAt); System.out.println("compareTo = " + compareTo); System.out.println("codePointBefore = " + codePointBefore); System.out.println("codePointCount = " + codePointCount); System.out.println("offsetByCodePoints = " + offsetByCodePoints); System.out.println("getBytes = " + Arrays.toString(getBytes)); System.out.println("toCharArray = " + Arrays.toString(toCharArray)); System.out.println("charAt = " + charAt); System.out.println("contains = " + contains); System.out.println("replaceAll = " + replaceAll); System.out.println("replace = " + replace); System.out.println("substring = " + substring); System.out.println("substring1 = " + substring1); System.out.println("endsWith = " + endsWith); System.out.println("startsWith = " + startsWith); System.out.println("split = " + Arrays.toString(split)); System.out.println("split1 = " + Arrays.toString(split1)); System.out.println("concat = " + concat); System.out.println("contentEquals = " + contentEquals); System.out.println("equalsIgnoreCase = " + equalsIgnoreCase); System.out.println("indexOf = " + indexOf); System.out.println("toLowerCase = " + toLowerCase); System.out.println("toUpperCase = " + toUpperCase); System.out.println("join = " + join); System.out.println("equals = " + equals); System.out.println("empty = " + empty); System.out.println("length = " + length); System.out.println("trim = " + trim); } 上述打印结果为: codePointAt = 49 compareTo = 16 codePointBefore = 103 codePointCount = 3 offsetByCodePoints = 11 getBytes = [97, 98, 99, 100, 101, 102, 103, 49, 50, 51, 52, 53, 54] toCharArray = [a, b, c, d, e, f, g, 1, 2, 3, 4, 5, 6] charAt = 1 contains = false replaceAll = abCdefg123456 replace = abcdefg一23456 substring = abc substring1 = efg123456 endsWith = true startsWith = false split = [ab, defg123456] split1 = [ab, defg123456] concat = abcdefg1234567890 contentEquals = false equalsIgnoreCase = true indexOf = -1 toLowerCase = abcdefg123456 toUpperCase = ABCDEFG123456 join = abcdefg123456,7890,AAA equals = false empty = false length = 13 trim = abc 以上为个人总结记录使用，希望能够帮助其他人，如有不足或错误欢迎大家指正。