JAVA学习—Java基本if语句（成绩划分）—2021.5.22

JAVA学习—Java基本if语句（成绩划分）—2021.5.22

第一个例子 以取绝对值为例

package a3;
/**
 * The use of if statement
 * @author hengyuzuo
 *
 */
public class Ifstatement {
	/**
	 * The entrance of the program
	 * @param args
	 */

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int tempNumber1, tempNumber2;
		
		//try a positive value
		tempNumber1 = 5;
		
		if (tempNumber1 >= 0) {
			tempNumber2 = tempNumber1;
		}else {
			tempNumber2 = -tempNumber1;
		}// Of if
		
		System.out.println("The absolute value of " + tempNumber1 + " is " + tempNumber2);
		
		//try a negative value
		tempNumber1 = -3;
		
		if (tempNumber1 >= 0) {
			tempNumber2 = tempNumber1;
		}else {
			tempNumber2 = -tempNumber1;
		}// Of if
		
		System.out.println("The absolute value of " + tempNumber1 + " is " + tempNumber2);
		
		// Now we use a method/function for this purpose.
		tempNumber1 = 6;
		System.out.println("The absolute value of " + tempNumber1 + " is " + Math.abs(tempNumber1));
		tempNumber1 = -8;
		System.out.println("The absolute value of " + tempNumber1 + " is " + Math.abs(tempNumber1));
	} // Of main
	
	/**
	 * The absolute value of the given parameter.
	 * 
	 */
	public static int abs(int paraValue) {
		if (paraValue >= 0) {
			return paraValue;
		}else{
			return -paraValue;
		}// Of if
	}// Of abs		
}// Of class Ifstatement	

运行结果，完成！

The absolute value of 5 is 5
The absolute value of -3 is 3
The absolute value of 6 is 6
The absolute value of -8 is 8

问题：

tempNumber1 = 6;
		System.out.println("The absolute value of " + tempNumber1 + " is " + abs(tempNumber2));
		tempNumber1 = -8;
		System.out.println("The absolute value of " + tempNumber1 + " is " + abs(tempNumber1));
	}// Of main

此时说我未定义

更改后解决

System.out.println("The absolute value of " + tempNumber1 + " is " + Math.abs(tempNumber2));

第二个例子 以划分成绩为例

介绍
键盘输入一个考试成绩（0-100），进行等级划分：
优秀：90-100
良好：80-90
中等：70-80
及格：60-70
不及格：60以下

代码

package test1;
import java.util.Scanner;

/**
 * 
 * @author hengyuzuo
 *
 */
public class TestDemo1 {
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("请输入考试成绩：");
		int score = sc.nextInt();
		
		if( score >= 90 && score <=100 ) {
			System.out.println("优秀啊");
		}else if ( score >= 80 && score < 90) {
			System.out.println("良好啊");
		}else if ( score >= 70 && score < 80) {
			System.out.println("中等啊");
		}else if ( score >= 60 && score < 70) {
			System.out.println("及格啊");
		}else if ( score >= 0 && score < 60) {
			System.out.println("不及格啊");
		}else
			System.out.println("输入非法");
		
	}// Of main
}// of TestDemo1 class

运行结果

请输入考试成绩：
111
输入非法