String类方法:
toUpperCase字母转大写
toLowerCase字母转小写
indexOf()查找包含的内容
substring(开始截取索引,结束索引)字符串截取
案例:
public class StringTest { public static void main(String[] args) { getCount("38uYrrwEE"); System.out.println(toConvert("adsdwDDS")); String[] arr = {"hellojava","nihaojava","baijavadu","jijisss","234sdassd"}; String[] str = selectString(arr,"java"); for (int i = 0; i < str.length; i++) { System.out.println(str[i]); } } public static String[] selectString(String[] str,String key){ //记录出现的次数 int index = 0; //定义字符串数组记录包含关键字的元素 String[] arr2 = new String[str.length]; for (int i = 0; i < str.length; i++) { if(str[i].indexOf(key) != -1){ arr2[index] = str[i]; index++; } } //定义字符串数组记录符合要求的元素并去除多余元素 String[] arr = new String[index]; for (int i = 0; i < arr.length; i++) { arr[i] = arr2[i]; } return arr; } public static String toConvert(String str){ String first = str.substring(0,1); String after = str.substring(1); first = first.toUpperCase();//转换大写函数 after = after.toLowerCase();//转换小写函数 return first + after; } public static void getCount(String str) { int big = 0; int small = 0; int number = 0; for (int i = 0; i < str.length(); i++) { char c = str.charAt(i); if(c >= 'A' && c <= 'Z'){ big++; } else if(c >= 'a' && c <= 'z'){ small++; } else if(c >= 0 && c <= '9'){ number++; } } System.out.println(big + " " + small + " " + number); } }
StringBuffer类方法:
toString()将缓冲区内所有字符变为一个字符串
reverse()将缓冲区内的字符进行翻转
replace(int start,int end,String str)
将指定范围的字符串替换为新的字符串
insert(int index,任意类型) 为指定所有index添加任意类型的值
delete(int start,int end) 删除字符串从start到end
方法append() 追加字符串
案例:
public class StringBufferTest { public static void main(String[] args) { function(); function_1(); insertBuffer(); function_2(); function_3(); function_4(); } public static void function_4(){ StringBuffer buffer = new StringBuffer(); buffer.append("abcdef"); buffer.append(12345); String s = buffer.toString(); System.out.println(s); } public static void function_3(){ StringBuffer buffer = new StringBuffer(); buffer.append("abcdef"); buffer.reverse(); System.out.println(buffer); } public static void function_2(){ StringBuffer buffer = new StringBuffer(); buffer.append("abcdef"); buffer.replace(1,4,"Q"); System.out.println(buffer); } public static void insertBuffer(){ StringBuffer buffer = new StringBuffer(); buffer.append("abcdef"); buffer.insert(4,00.2); System.out.println(buffer); } public static void function_1(){ StringBuffer buffer = new StringBuffer(); buffer.append("abcmdf"); buffer.delete(1,buffer.length()); System.out.println(buffer); } public static void function() { StringBuffer buffer = new StringBuffer(); buffer.append("20").append(1).append(31).append(1.33); //buffer.append("20",3,2); System.out.println(buffer); } }