"Java Programming Thought" Notes Chapter 4 Controlling the Execution Process

1. true and false

1.1 if--else if--else, while, do--while all use the truth or falsehood of the conditional expression to determine the execution path.

1.2 Java does not allow numbers to be used as true or false judgments, C and C++ can be either 0 or true.

2.Math.random()

• Yields a double value [ 0, 1 ) including 0 and excluding 1.

3.foreach syntax

• For example, for(float x: f){ } f is an array, any method that returns an array can use foreach

4.return 

• return causes the current method to exit, returning the value.
• Except for the constructor, any method has a return value type such as void fun(), String fun(), void fun(), no need to write return, there is return by default, other methods must have a return value (or an expression produces a value )

5.break和continue

• break terminates the current layer loop and exits the loop, continue terminates the current layer loop and enters the next loop.

5.1 Label: Use when you want to jump out of nested loops

continue leaf;//Jump to the loop where the label is located to start recirculating, note that i will not increase in the inner loop, // break leaf; jump out of the loop where the label is located, no longer loop, and inner i will not increase

		bed:
		// No other code can be added between the label and the iterator
		for (j = 0; j < 5; j++) {
			System.out.println("外");
			for (; i < 10; i++) {
				if (i == 6) {
					
					continue leab;
					// break leab;
				}
				System.out.println("nei");
			}
		}

6. switch(value) 

		switch(i){ //
		case 1: System.out.println(1);break;
		case 2: System.out.println(1);
		case 'a': System.out.println(97);break; // char 'a' is automatically converted to ASCII
		}