java字符与字符串String & char

清疚 2022-02-23 01:26 243阅读 0赞

## 字符串拼接 ##

java允许用+号来拼接两个字符串  
![在这里插入图片描述][2019040519263025.png]  
这种特性也经常用在输出语句中

System.out.println("The answer is" + answer);

## 字符串不可变 ##

和python一样，java的字符串也是不可变的。  
但是我么你可以采用substring方法  
![在这里插入图片描述][20190405192855567.png]

## 检测字符串是否相等 ##

![在这里插入图片描述][20190405192956292.png]

## 字符串长度，判断空串 ##

![在这里插入图片描述][20190405193026741.png]

## String API ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 1]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 2]

## 构建字符串 ##

可以采用StringBuilder类来构建字符串

public class stringBuilder { 
        public static void main(String[] arg) { 
            StringBuilder builder = new StringBuilder();
            builder.append('c');
            builder.append("cdef");
            System.out.println(builder.length());   //builder的长度
            String str = builder.toString();
            System.out.println(str);
            System.out.println(str.length());
        }
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 3]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 4]

[2019040519263025.png]: /images/20220223/420d50befbfa4797bb5086e21c6a0f2d.png
[20190405192855567.png]: /images/20220223/cb6d1071707c49498055755b24af0e29.png
[20190405192956292.png]: /images/20220223/78a08bec972e433c81448644578414d2.png
[20190405193026741.png]: /images/20220223/8c4e2d9a426742baa37e614308ce67a0.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70]: /images/20220223/efcd9f69e5f74fdd87a026b93ce30023.png
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 2]: /images/20220223/aae6f0cd4e724e578c096457dacfe17b.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 3]: /images/20220223/3ac13c3cd0d94804ba27c5fefc428771.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl8zNjM3Mjg3OQ_size_16_color_FFFFFF_t_70 4]: /images/20220223/1ea7993010c0470fb6ff5b6ca78f7488.png