Note: The below answers apply to mainland Mandarin Chinese. For technical vocabulary, the words used in different regions often have differences. The link you posted in your comment looks like it uses Taiwan standards.
- Class 类
- Object 对象
- Instance 实例
- Attribute 属性
- Method 方法
"Object oriented" is 面向对象. You can find more at the 面向对象程序设计 Chinese Wikipedia page.