java的字符串转换

古城微笑少年丶 2024-03-22 14:11 63阅读 0赞

1.数值转字符串  
注意：这里的转换并不是按照ASCII进行转换，而是直接变成字符形式  
![在这里插入图片描述][57888273fc7c4ea2a45d130316a09811.png]

public class Test {
        
        public static void main(String[] args) {
        
            String str1 = String.valueOf(1234);
            String str2 = String.valueOf(12.34f);
            String str3 = String.valueOf(false);
            String str4 = String.valueOf('1');
            String str5 = String.valueOf("1234");
            String str6 = String.valueOf(12.34);
            char[] arr = {
        'a','b'};
            String str7 = String.valueOf(arr);
            System.out.println(str1);
            System.out.println(str2);
            System.out.println(str3);
            System.out.println(str4);
            System.out.println(str5);
            System.out.println(str6);
            System.out.println(str7);
        }
    }

![在这里插入图片描述][5764b1bd17014856b9dccedddf1f74c1.png]

2.字符串转数字

// 字符串转数字
    // 注意：Integer、Double等是Java中的包装类型，这个后面会讲到
    int data1 = Integer.parseInt("1234");
    double data2 = Double.parseDouble("12.34");
    System.out.println(data1);
    System.out.println(data2);

![在这里插入图片描述][ff74037b22954b2ba16706a44d9fd50b.png]  
注：有关包装类的知识，可以去看https://blog.csdn.net/qq\_53312143/article/details/126124615这位博主的博客

3.大小写转换

public class Test {
        
        public static void main(String[] args) {
        
            String str1 = "HELLO,你好";
            String str2 = "hello,你好";
            String str3 = "HEllo";
            System.out.println(str2.toLowerCase());//转换成小写
            System.out.println(str2.toUpperCase());//转换成大写
            System.out.println(str3.toLowerCase());
        }
    }

4.字符串转数组

public class Test {
        
        public static void main(String[] args) {
        
            String s = "hello";
    // 字符串转数组
            char[] ch = s.toCharArray();//toCharArray()字符串转化为字符数组
            System.out.println(Arrays.toString(ch));
            System.out.println();
    // 数组转字符串
            System.out.println(s+"");//可以使用变量名+““的形式，将这个变量输出为字符型
            String s2 = new String(ch);
            System.out.println(s2);//或者用String方法，转换
        }
    }

![在这里插入图片描述][8ef6e3589a5e41c797124bad42aad145.png]

5.格式化  
一般用于输出打印上

public class Test {
        
        public static void main(String[] args) {
        
            String str1 = String.format("%d-%d-%d",2019,9,14);
            System.out.println(str1);
        }
    }

![在这里插入图片描述][790795ffdf5f49f08a90591ad47ed4dc.png]

[57888273fc7c4ea2a45d130316a09811.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/75f5fb31532b448c940061f01ebe16f1.png
[5764b1bd17014856b9dccedddf1f74c1.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/5c555919884d49feaa6f0b262f50a2c4.png
[ff74037b22954b2ba16706a44d9fd50b.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/e5738beec4f94512bde276566c6e3d08.png
[8ef6e3589a5e41c797124bad42aad145.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/31018d61d1e94c299f4fb38e84ac123b.png
[790795ffdf5f49f08a90591ad47ed4dc.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/22/1e8213fab7c7437d9ef6bff4b6f66d1f.png