A company H has written knowledge points and written knowledge points.

A company H has written knowledge points and written knowledge points.

1. Integer I = new Integer (3 );

Switch (I ){

Case 1:

System. out. println (I );

Break;

Case 3:

System. out. println (I );

Break;

Default:

System. out. println ("error ");

Break;

}

What will happen to the above Code: Compilation error, output 3, and output error.

Analysis: I thought about it. According to the definition, the data in the switch can only be byte, char, short, int, and the new String type. Integer is the packaging class, there is a big difference with the types mentioned above. Therefore, according to the principle, an error will be reported during compilation. Unless the Integer intValue () function is used to return an int type, an exception will occur. However, after compiling and running in eclipse, we found that the output result was 3, and no error was reported. I suddenly felt unscientific. after the class is decompiled, the switch is changed to I. intValue (), that is, the compiler automatically compiles the packaging class object into I. intValue (), which is an integer, so it can run normally.

So what is the answer to this question? I think the logic is wrong, but eclipse compilation has passed? Do you have any explanation for the root cause.

2. Access scope of java classes when public, default, protected, and private are used.

3. What are java generics and what are their advantages over other languages.

Generic is a wide range of types. The types are unrestricted. containers can load any type of data.

4. What is the difference between two types of traffic and word throttling? What are the classes involved.

The minimum unit of byte stream is byte, the minimum unit of byte stream is character, and the byte stream has a wide range. Byte stream-related classes include InputStream, FileInputStream, OutputStream, and FileOutputStream. Stream-related classes include writer, FileWriter, Reader, and FileReader.

5. Use java to implement the quick Rank Algorithm.

6. multi-thread java. Two threads are used for cross-output strings, and thread communication is required.

7. does not belong to java synchronous functions. wait () sleep () uses Y () lock ().

8. Write an SQL statement to select the top three boys and girls respectively.

Analysis: This question is mainly about the union keyword. An SQL statement is used to select the top three students of both men and women (select name, gender, grade from stu order by grade where gender = 'male' limit) union (select name, gender, grade from stu order by grade where gender = 'famale' limit)

9. Why does the application get stuck when gc is called? What are gc tuning.

Analysis: This question requires the basic knowledge of gc, otherwise it cannot be answered. The jvm memory is divided into four areas: heap zone, stack zone, local method zone, method zone, and heap zone, which are divided into many areas, new generation zone, persistent zone, and old generation zone, most threads are mostly in the new generation zone for a short time. The threads in the new generation zone of gc are frequent, and the time is short. The threads that are not gc will be moved into the next zone, in the end, there will be a few threads in the old generation area. The threads in the old generation area are complicated and gc is very slow. Therefore, when gc is sent to the threads in the old generation area, the time will be a little longer, this is a choppy phenomenon. However, the gc frequency of the old generation is small, so sometimes it gets stuck.

The stack area contains temporary variables and intermediate results. The local method area supports the native method and stores the call status of each native method. The method area contains information about loading classes, static variables and final variables.

10. Basic jvm knowledge.

11. String inversion.

Refer to the reverse () function of StringBuffer

12. Remove repeated characters in the string when the original character order remains unchanged.

Store it in the TreeSet and retrieve it. This is the most concise method currently known.

Bachelor's degree in digital model electric interview written test knowledge

1. What is the content of kilhov's theorem? (Shi LAN Microelectronics)

2. Flat capacitor formula (C = ε S/4 π kd ). (Unknown)

3. The most basic characteristics, such as the transistor curve. (Unknown)

4. Describe the concept of feedback circuit and list their applications. (Shi LAN Microelectronics)

5. Negative Feedback types (voltage feedback, current feedback, voltage feedback and current feedback); negative feedback advantages (reducing the gain sensitivity of the amplifier, changes the input and output resistors, improves the linearity and nonlinear distortion of the amplifier, and effectively extends the passband of the amplifier for automatic adjustment) (unknown)

6. What is the purpose of frequency compensation for a amplifying circuit? (Shi LAN Microelectronics)

7. Frequency response, for example, several methods to change the frequency response curve. (Unknown)

8. Provide a checkpoint Op Amplifier, how to compensate the phase, and draw the Potter diagram after compensation. (Concave and convex)

9. Basic amplifier circuit types (voltage amplifier, current amplifier, reciprocal amplifier and mutual resistance amplifier)

Point, especially the reason that the differential structure is widely used. (Unknown)

10. A differential circuit is provided to tell the output voltage Y + and Y-to calculate the common mode component and differential mode component. (Unknown)

11. Two input tubes for poor picture placement. (Concave and convex)

12. Draw the circuit schematic diagram of addition, subtraction, differentiation, and integral operation composed of Op-ops. And draw a transistor-level Op Amplifier Circuit. (Shi LAN Microelectronics)

13. Use an operational amplifier to form a 10-fold amplifier. (Unknown)

14. A simple circuit is provided, which allows you to analyze the output voltage characteristics (that is, an integrated circuit) and obtain the rise/fall time at a certain point on the output end. (Infineon test questions)

15. resistor R and capacitor C are connected in series. The input voltage is the voltage between R and C, and the output voltage is the upper voltage of C and the power-on voltage of R respectively.

Pressure, need to draw the frequency spectrum of the input voltage of these two circuits, determine what these two circuits are Qualcomm filter, what is low-pass filter

Wave. What are the principles and differences between RC <16? Active Filter and passive filter? (Xintai hardware)

17. There is a time-domain signal S = V0sin (2pif0t) + V1cos (2pif1t) + V2sin (2pif3t + 90), when it passes through the low-pass, band-pass, high-pass filter signal representation. (Unknown)

18. What should I consider when selecting resistance? (Dongxin pen exam)

19. In a CMOS circuit, a single tube must be used as a switch to accurately transmit analog low-level data. You can use a P or N tube for this single tube. Why? (Shi LAN Microelectronics)

20. A circuit consisting of multiple MOS tubes is provided to calculate the voltage at 5 points. (Infineon test questions)

21. voltage sources and current sources are frequently used modules in integrated circuits. Please draw the line structure you know and briefly describe its advantages and disadvantages. (Shi LAN Microelectronics)

22. Draw and explain the Generating Circuit of current offset. (Concave and convex)

23. Smith circuit, calculate the return voltage. (Huawei interview questions)

24. Crystal Oscillator. It seems that the oscillator frequency is given for you to calculate the cycle (it should be a single-chip microcomputer, one of 12 cycles...) (Huawei interview questions)

25. Which of the following three-point Oscillator Circuits are available for LC sine wave oscillator. (Shi LAN Microelectronics)

26. What is VCO and what parameters (voltage controlled oscillator ?) (Huawei interview questions)

27. What are the components of the Phase-Locked Loop? (Shi LAN Microelectronics)

28. The phase-locked loop circuit is composed of an oscillator (for example, how to build a Oscillator with a D trigger ). (Unknown)

29. Find the output frequency of the Phase-Locked Loop and provide a structure of the Phase-Locked Loop. (Unknown)

30. If the company is engaged in high-frequency electronics, it may require RF knowledge, frequency modulation, and frequency identification. (Unknown)

31. An electrical source is connected to a transmission line (the length is L and the transmission time is T). The waveform at the terminal is drawn and the transmission line has no loss. Provide the power supply voltage waveform, and draw the terminal waveform. (Unknown)

32. Matching resistance of microwave circuit. (Unknown)

33. What are the methods for implementing DAC and ADC? (Shi LAN Microelectronics)

34. composition and working principle of A/D circuit. (Unknown)

35. Some technical knowledge required for actual work (it is easy to ask during the interview ). Such as low power consumption, stability, and high speed of the circuit

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What knowledge points are required for the C language test?

Pointers, arrays, and memory allocation are all relatively basic...