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);
}
}
转载于:https://www.cnblogs.com/release0/p/9196180.html
相关资源：JAVA上百实例源码以及开源项目
