if选择结构

if单选择结构

语句结构

if(condition)
   statement;

举例：

package struct;

import java.util.Scanner;

public class IfDemo01 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入内容：");
        String str = scanner.nextLine();

        //equals判断字符串是否相等
        if (str.equals("hello")) {
            System.out.println(str);
        }

        System.out.println("End");

        scanner.close();
    }
}

if双选择结构

语句结构

if (condition)
   statement1;
else
   statement2;

举例：

package struct;

import java.util.Scanner;
import java.util.zip.Inflater;

public class IfDemo02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入成绩：");
        int score = scanner.nextInt();
        if (score >= 60) {
            System.out.println("成绩合格");
        } else {
            System.out.println("成绩不合格");
        }

        scanner.close();
    }
}

if多选择结构

语句结构

if(condition)
   statement;
else if(condition)
   statement;
else if(condition)
   statement;
.
.
else 
   statement;

举例：

package struct;

import java.util.Scanner;

public class IfDemo03 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入成绩：");
        int score = scanner.nextInt();

        if (score <= 100 && score >= 90) {
            System.out.println("成绩为优秀");
        } else if (score < 90 && score >= 80) {
            System.out.println("成绩为良好");
        } else if (score < 80 && score >= 60) {
            System.out.println("成绩为合格");
        } else if (score < 60 && score >= 0) {
            System.out.println("成绩不合格");
        } else {
            System.out.println("输入的成绩不符合要求");
        }

        scanner.close();
    }
}