7.8-Java basic knowledge test-summary of error-prone questions

7.8-Java basic knowledge test-summary of error-prone questions

1. The command of the Java interpreter is (java) java HelloWorld class file to explain to the computer
2. Java compiler command (javac)---->javac HelloWorld.java
3. The development kit used by Java developers is (JDK)
4. Programs developed in Java language can be run on any platform (and do not require JRE)
5. All of the following are legal Java identifiers (B)
   A.09stu teacher $money
   B._salary post123 name
   C.case abstract final
   D.#ID list today
   Analysis: A number cannot be placed at the beginning, B is correct, C identifier It cannot be a keyword, and D cannot use the # symbol
6. final float PI = 3.14f;
   Analysis: Add F after the constant to indicate that it is of float type. If no F is added, the integer defaults to the int type, and the floating point number defaults to the double type.

public static void main(String[] args){
    
     
int x = 0; 
Scanner sc = new Scanner(System.in); 
x =sc.nextInt(); 
if(x--<5)
System.out.println(x); 
else
System.out.println(x++); 
} 

After running, if you enter 5 from the keyboard, the output result is ()

A.3 、 B.4 、 C.5 、 D.6

Analysis: a++, ++a, where the value of a will increase by 1,
but the overall value of a++ remains unchanged, the overall value of ++a is +1,
so a–<5, incorrect, execute else, but the value of a The value of -1 becomes 4, and the value of a– is still 4