public class HelloWorld { public static void main(String[] args) {
int age=25;
If ( age >= 60){
System. out. printLn( “老年”) ;
} else if (40<= age <60){
System. out. printLn( “中年”) ;
} else if ( 18<= age<40) {
System. out. printLn( “ 少年”) ;
} else (0< age < 18){
System. out. printLn( “ 儿童”);
}
}
}

public class HelloWorld { public static void main(String[] args) {
int age=25;
If ( age >= 60){
System. out. printLn( “老年”) ;
} else if (40<= age <60){
System. out. printLn( “中年”) ;
} else if ( 18<= age<40) {
System. out. printLn( “ 少年”) ;
} else (0< age < 18){
System. out. printLn( “ 儿童”)
}
}
}

if(age > 60){

        System.out.println("老年");

    }else if(age >= 40){

        System.out.println("中年");

    }else if(age >= 18){

        System.out.println("少年");

    }else{

        System.out.println("童年");

    }

不需要使用&&，if-else语句是逐步判断的，在 if(age > 60) 就已经将age可能的值根据60划为两类