i?>=?0?&&?a?>?3

你的a等于0，不滿足條件，不執行循環。應該這么寫：

import?java.util.Arrays;
public?class?HelloWorld?{
????
????//完成?main?方法
????public?static?void?main(String[]?args)?{
???????HelloWorld?score?=?new?HelloWorld();
???????int[]?scores?=?{89,-23,64,91,119,52,73};
????????System.out.println("前三名成績是：");
????????score.so(scores);
????}
????
????//定義方法完成成績排序并輸出前三名的功能
???public?void?so(int[]?scores)
???{
???????Arrays.sort(scores);
???????int?a=0;
	???for(int?i?=?scores.length-1;i>=0;i--){
		???if(scores[i]<0||scores[i]>100){
			???continue;
		???}
		???while?(a?<?3)?{
				a++;
				System.out.println(scores[i]);
				break;
		???}
	???}
???}
}