What I learned in Java (Part 3) Instruction execution statement

Looking back on Java

Last time I posted about variables in Java. Please see that article if you like. What I learned in Java (Part 2) What are variables

This time I would like to write about the statement of instruction execution.

What is an instruction execution statement?

An instruction execution statement is an instruction statement prepared by Java from the beginning. As a basic form of instruction execution statement

Statement to call (argument)

It will be. * Information in parentheses is called an argument (hikisu) or parameter.

Display to console

As one of the concrete ones, "System.out.println ()" used in previous articles etc.

public class Main {
	public static void main(String[] args) {
		System.out.println("Hello");
	}
}

Execution result This is a statement to display the arguments enclosed in parentheses on the screen. There is also a difference between "System.out.println ();" and "System.out.print ();".

public class Main {
	public static void main(String[] args) {
		//new line
		System.out.println("Nice to meet you");
		System.out.println("Hello");
		
		//No line breaks
		System.out.print("Nice to meet you");
		System.out.print("Hello");
	}
}

Execution result It is also possible to use with variables

public class Main {
	public static void main(String[] args) {
		//Variable declaration, assignment
		int a = 1;
		String b = "Hello";
		
		//Display variables
		System.out.println(a);
		System.out.println(b);
	}
}

Execution result

Comparison of two values

Instructions for comparing two values

int m = Math.max(a,b);

This is an instruction to compare "a" and "b" specified by the argument and assign the larger one to the variable "m".

public class Main {
	public static void main(String[] args) {
		//Variable declaration, assignment
		int a = 1;
		int b = 2;
		
		//Substitute the larger of a and b into the variable m
		int m = Math.max(a, b);
		
		//Show assigned value
		System.out.println(m);
	}
}

Execution result

Convert strings to numbers

Converts a number entered in a String type variable to an integer

int seisu = 1;
String moziretu = "1";

The contents "1" of the two variables created above are completely different. Integers cannot be calculated with the character string "1" assigned to the String type. Therefore, the statement for converting a String type number to an int type (integer) is as follows.

int n = Integer.parseInt(moziretu);

Example

public class Main {
	public static void main(String[] args) {
		//Substitute "1" for each of int type and String type
		int seisu = 1;
		String moziretu = "1";
		//Display by adding int type and String type
		System.out.println(seisu + moziretu);
		
		//Convert String type to int type
		int n = Integer.parseInt(moziretu);
		//After conversion, calculate and display between int types
		System.out.println(seisu + n);
	}
}

Execution result As you can see from the execution result, the first line is the state where the integer "1" and the character string "1" are lined up side by side, and the second line converts the character string "1" to an integer and the calculation result between the integers. Is displayed.

Instructions to create random numbers

Instructions to generate random numbers like dice

int r = new java.util.Random().nextInt(10);

In the above, a random number from 0 to 9 is assigned to the variable r. Example

public class Main {
	public static void main(String[] args) {
		//0 for int type r~Generate and substitute random numbers up to 9
		int r = new java.util.Random().nextInt(10);
		//Display the variable r
		System.out.println(r);
	}
}

Execution result (randomly generated numbers are assigned) It is also possible to range.

public class Main {
	public static void main(String[] args) {
		//0 for int type r~Generate and substitute random numbers up to 9
		int r = new java.util.Random().nextInt(10) + 10;
		//Display the variable r
		System.out.println(r);
	}
}

Execution result (random numbers from 10 to 19 are assigned)

Command to receive input from the keyboard

Accepts input of strings or integers from the keyboard

//Receive a string
String input1 = new java.util.Scanner(System.in).nextLine();
//Receive an integer
int input2 = new java.util.Scanner(System.in).nextInt();

Example

public class Main {
	public static void main(String[] args) {
		System.out.println("Please enter the product you purchased");
		String input1 = new java.util.Scanner(System.in).nextLine();
		
		System.out.println("Please enter the number of purchases");
		int input2 = new java.util.Scanner(System.in).nextInt();
		
		System.out.println(input1 + "To" + input2 + "It's an individual. Thank you for your purchase.");
	}
}

Execution result I tried to summarize the basic instruction execution statements.

References

https://book.impress.co.jp/books/1113101090

Next time, I would like to write about conditional branching and repetition.