Java.lang.String提供的常用的方法

1.字符串的大小写转换

(1).都转换为大写：toUpperCase();

(2).都转换为小写：toLowerCase();

package com.cal.string;
/**
* 将字符串转换为全大写toUpperCase()
* 将字符串转换为全小写toLowerCase()
* @author lenovo
*
*/
public class Test06 {
public static void method(){
String s = " Hello Java ";
sop(s.toLowerCase());
sop(s.toUpperCase());
}

public static void main(String[] args) {
method();
}

public static void sop(String s){
System.out.println(s);
}

}

结果：   hello java    HELLO JAVA    

2.字符串去除两端的空格：trim();
package com.cal.string;
/**
* 将字符串转换为全大写toUpperCase()
* 将字符串转换为全小写toLowerCase()
* 将字符串前面和后面的空格去掉trim()
* @author lenovo
*
*/
public class Test06 {
public static void method(){
String s = " Hello Java ";
sop(s.trim());
}

public static void main(String[] args) {
method();
}

public static void sop(String s){
System.out.println(s);
}

}

结果：Hello Java

3.字符串的切割：spilt();
package com.cal.string;
/**
* 获取字符串的切割
* @author lenovo
*
*/
public class Test04 {
public static void method(){
String s = "zhangsan,lisi,wangwu";
String[] arr = s.split(",");

for(int i=0;i<arr.length;i++){
sop(arr[i]);
}
}

public static void main(String[] args) {
method();
}

public static void sop(String arr){
System.out.println(arr);
}

}

结果：zhangsan lisi wangwu

4.获取子串：substring();  substring(start,end);
package com.cal.string;
/**
* 获取子串
* @author lenovo
*
*/
public class Test05 {
public static void method(){
String s = "abcdefg";
sop(s.substring(3));
sop(s.substring(3, 6));//包含头，不包含尾
}

public static void main(String[] args) {
method();
}

public static void sop(String s){
System.out.println(s);
}
}

结果：defg  def

5.字符串的替换：replace(oldchar,newchar);
package com.cal.string;
/**
* 字符串的替换
* @author lenovo
*
*/
public class Test03 {
public static void method(){
String s = "Hello Java";
//String a = s.replace("m", "n");//如果要替换的字符不存在，则返回的是原串
String b = s.replace("Java", "World");
sop(b);
}

public static void main(String[] args) {
method();
}

public static void sop(String s){
System.out.println(s);
}
}
6.将字符数字转换为字符串：string(char[]);
package com.cal.string;
/**
* 字符串的转换
* @author lenovo
*
*/
public class Test02 {
public static void method(){
char[] arr = {'a','b','c','d','e','f'};
String a = new String(arr);
sop(a);
}

public static void main(String[] args) {
//将字符数组转换成字符串
method();
}

public static void sop(String str){
System.out.println(str);
}
}

结果：abcdef

7.将字符串转换为字符数组toCharArray();
package com.cal.string;
/**
* 字符串的转换
* @author lenovo
*
*/
public class Test02 {
public static void method(){
String b = "abcsdnfbhr";
char[] ar = b.toCharArray();
for(int i=0;i<ar.length;i++){
soop(ar[i]);
}
}

public static void main(String[] args) {
//将字符数组转换成字符串
method();
}

public static void soop(char i){
System.out.println(i);
}

}

结果：

a
b
c
s
d
n
f
b
h
r