整数类型
byte，字节 【1字节】表示范围:-128~127即: -2^7~2^7 -1
short，短整型 【2字节】表示范围: -32768~32767
int，整型 【4字节】表示范围: -2147483648~2147483647
long,长整型 【8字节】表示范围: -9223372036854775808 ~ 9223372036854775807
class Num {public static void main(String[] args) {byte v1 = 32;short v2 = 10000;int v3 = 12345678;long v4 = 3452354265452L;}
}
byte字节类型
java 有符号 -128 ~ 127 负数+256转换python
python 有符号 0 ~ 255
class NewByte {public static void main(String[] args) {String name = "李白";byte[] data = name.getBytes(StandardCharsets.UTF_8);System.out.println(Arrays.toString(data));}
}
字符串
class NewStr {public static void main(String[] args) {// 定义字符串的方法String v1 = "李白";String v2 = new String("李白");String v3 = new String(new byte[]{-26, -99, -114, -25, -103, -67});String v5 = new String(new char[]{'李', '白'});// 字符串操作String str1 = " 这是一个You趣DE 故事 ";char v10 = str1.charAt(5); //下标取字符串中的某个元素int len = str1.length(); //取字符串长度for (int i = 0; i < len; i++) {char item = str1.charAt(i); //循环字符串中每个元素}String v11 = str1.trim(); //取出字符串两侧空白String v12 = str1.toLowerCase(); //字母全部转小写String v13 = str1.toUpperCase(); //字母全转大写String[] v14 = str1.split("趣"); //分割符System.out.println(Arrays.toString(v14)); // Arrays.toString()打印数组String v15 = str1.replace("Y", "M"); //替换符String v16 = str1.substring(2, 4); //切片[2:4]boolean v17 = str1.equals("下雨了"); //判断字符串是否相等 结果true或falseboolean v18 = str1.contains("趣"); //判断是否包含某个元素boolean v19 = str1.startsWith(" "); //判断以什么开头String v20 = str1.concat("what are you doing?"); //字符串尾部添加System.out.println(v20);//StringBuilder str2 = new StringBuilder(); //创建可变的空字符串对象str2.append("大河之剑");str2.append("天上来");str2.append("！！！");String dataString = str2.toString(); //将StringBuilder对象str2中的内容转换为普通的不可变字符串对象System.out.println(dataString);}
}
Array数组 固定长度 特定类型
class NewArray {public static void Array1(String[] args) {// 定义一个整型数组，限制元素个数3个int[] numArray = new int[3];numArray[0] = 123;numArray[1] = 456;numArray[2] = 789;System.out.println(Arrays.toString(numArray)); //[123, 456, 789]//定义字符串数组// 方法1,String[] names = new String[]{"李白", "孙尚香", "诸葛亮"};System.out.println(Arrays.toString(names));// 方法2,String[] nameArray = {"李白", "孙尚香", "诸葛亮"};System.out.println(Arrays.toString(nameArray));// 循环数组,for (int idx = 0; idx < nameArray.length; idx++) {String item = nameArray[idx];System.out.println(item);}}public static void Array2(String[] args) {// ArrayListArrayList<String> nameList = new ArrayList<>(Arrays.asList("李白", "赵德汉", "秦叔宝"));// 添加一个元素nameList.add("程咬金");// 添加一个数组ArrayList<String> nameList2 = new ArrayList<>(Arrays.asList("蓝天", "白云"));nameList.addAll(nameList2);System.out.println(nameList);}public static void main(String[] args) {//Object类型（父类） 泛指子类 得到数组多样化Object[] array1 = {"哪吒", "孙悟空", 33, 99};int num = (int) array1[2];System.out.println(num);}
}
)
