Date: February 27, 2023

Topic: Primitive Type and Operators

Recall

Class 00

Class 01

2‘ complement

Primitive Type

进位制

Operators and precedence

Type Conversion

Notes

• Java运行顺序：从mian函数为起点，从上到下，从左到右

• System.out.print(打印内容)，在IDE里简写为sout

• System.out.println()表示每打印一个自动换行

• bit：一个最小0/1单元

• byte：8 bits，计算机最小操作单元

• 2的补码，对于负数：按位取反后加一

• 假如有n bits，可以表达2^n个数，max: 2^(n-1)-1, min: 2^(n-1)

除了这八种Primitive type外，其他的都叫Reference type：objects stored in heap(operated by references)

• byte, boolean | short, char | float, int | long, double

• In Java, when there is decimals, down cast to the closest integer.

• 两个’ ‘之间有且仅有一个字符，不能为空。single quote is char

• double quote is string.

• 123 |⇒ decimal

• 0123 |⇒ oct

• 0x123 |⇒ hex

• 0b101 |⇒ bin

• 符号的意思

++在后，先赋值后自加，++在前，先自加后赋值。

• ! logical negation
• tilde~按位取反
• && AND: true && true == true, false && false == false
• | | OR: true | | false == true, false | | false == false
• 运算顺序：NOT AND OR
• ternary operator:

• Explicit conversion: eg. double x = 1.9; int y = (int) x;
• Implicit conversion: eg. int x = 1; double y = x;

精度低的type 到精度高的type conversion可以不加（type）

<aside> 📌 SUMMARY:

</aside>

Date: March 1, 2023

Topic: 1D/ 2D Array + Class/Object

<aside> 📌 SUMMARY: 0 假空，所有的primitive type default是 0, (byte, short, int, long: 0; float, double: 0.0; chart: ‘0’) array default是 0，boolean default 是false， reference type default是 null。

</aside>

Date: March 2, 2023

Topic: Class & Objects 2&3

<aside> 📌 SUMMARY: 打印一个int[] result, System.out.println(Arrays.toString(result));

</aside>

Date: March 10, 2023