常用类03/String的转换⭐

川长思鸟来 2023-10-04 16:43 60阅读 0赞

## String的转换 ##

--------------------

### 1. String与基本数据类型包装类的转换 ###

1.  String–>基本数据类型、包装类:**调用包装类的静态方法: parseXxx ( str)**
2.  基本数据类型、包装类–> String:**调用string重载的value0f(xxx)**

package com.cyl;
    
    import org.junit.Test;
    
    public class StringMethodTest {
        
    
        @Test
        public void test(){
        
    
            String str1 = "123";
            //int num = (int)str1; 错误！
    
            int num = Integer.parseInt(str1);//123
            String str2 = String.valueOf(num); //"123"
            String str3 = num+"45";
    
            System.out.println(str1);
            System.out.println(str2);
            System.out.println(str3);
            System.out.println(str1 == str2);
        }
    }

> 结果

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70]

--------------------

### string 与char\[\]之间的转换 ###

> string–>char\[ \]:调用string的tocharArray()

package com.cyl;
    
    import org.junit.Test;
    
    public class StringMethodTest {
        
    
        @Test
        public void test(){
        
            String str1 = "abc123";
    
            char[] charArray = str1.toCharArray();
            for(int i = 0;i < charArray.length;i++){
        
                System.out.println(charArray[i]);
            }
        }
    }

> 结果  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 1]

> char\[\] --> string:调用string的构造器

package com.cyl;
    
    import org.junit.Test;
    
    public class StringMethodTest {
        
    
        @Test
        public void test(){
        
            char[] arr = new char[]{
        'h','e','l','l','o'};
            String str2 = new String(arr);
            System.out.println(str2);
        }
    }

> 结果

![在这里插入图片描述][3a76d1869fe64ff9bbe8beb7b5745571.png]

--------------------

### 2. String与byte\[\]之间的转换 ###

> 编码:字符串–>字节（看得懂—>看不懂的二进制数据)  
> 解码:编码的逆过程，字节–〉字符串―(看不懂的二进制数据—>看得懂>)

注：UnsupportedEncodingException ————>转码异常！！

> 编码：String --> byte\[\]:调用string 的getBytes()

package com.cyl;
    
    import org.junit.Test;
    
    import java.io.UnsupportedEncodingException;
    import java.util.Arrays;
    
    public class StringMethodTest {
        
    
        @Test
        public void test() throws UnsupportedEncodingException {
        
            String str1 = "abc123";
            byte[] bytes = str1.getBytes();//使用默认的字符集，进行转换
            System.out.println(Arrays.toString(bytes));
    
            String str2 = "中国";
            byte[] bytes1 = str2.getBytes();//使用默认的字符集，进行转换
            byte[] gbks = str2.getBytes("gbk");//使用gbk字符集进行编码
            System.out.println(Arrays.toString(bytes1));
            System.out.println(Arrays.toString(gbks));
        }
    }

> 结果

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 2]

> 解码: byte\[\] --> string:调用string的构造器

package com.cyl;
    
    import org.junit.Test;
    
    import java.io.UnsupportedEncodingException;
    import java.util.Arrays;
    
    public class StringMethodTest {
        
    
        @Test
        public void test() throws UnsupportedEncodingException {
        
            String str1 = "中国";
    
            //编码1
            byte[] bytes = str1.getBytes();//使用默认的字符集，进行转换
            //编码2
            byte[] gbks = str1.getBytes("gbk");//使用gbk字符集进行编码
            System.out.println(Arrays.toString(bytes));
            //解码
            String str2 = new String(bytes);//使用默认的字符串，进行解码。
            System.out.println(str2);
    
            String str3 = new String(gbks);
            System.out.println(str3);//出现乱码，因为编码集和解码集不一致
    
            String str4 = new String(gbks,"gbk");
            System.out.println(str4);
    
        }
    }

> 结果

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 3]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/42792188e92f47e98d113f4ce967d9e6.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/c97e96534ecc4ac7b2267d64760fe1f1.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70
[3a76d1869fe64ff9bbe8beb7b5745571.png]: https://img-blog.csdnimg.cn/3a76d1869fe64ff9bbe8beb7b5745571.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/70bf1803b6f748f0b3f22e1b97fdb584.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/53ba220596e24461b5fc5a05f962bfbe.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80ODA2MzY2MA==,size_16,color_FFFFFF,t_70