public?class?HelloWorld?{
????public?static?void?main(String[]?args)?{
????????int?age=25;
????????if(age>=60){
????????????System.out.println("老年");
????????}else?if(40<=age?&&?age<60){
????????????System.out.println("中年");
????????}else?if(18<=age?&&?age<40){
????????????System.out.println("少年");
????????}else?if(0<age?&&?age<18){
????????????System.out.println("童年");
????????}
????}
?}

這樣改完就可以了，但是呢，實際上還可以改成下面這樣↓

public?class?HelloWorld?{
????public?static?void?main(String[]?args)?{
????????int?age=25;
????????if(age>=60){
????????????System.out.println("老年");
????????}else?if(40<=age){
????????????System.out.println("中年");
????????}else?if(18<=age){
????????????System.out.println("少年");
????????}else?if(0<age){
????????????System.out.println("童年");
????????}
????}
?}

如果第一個if沒有過去，自然會自帶小于60的，沒必要在后面條件再寫了。