List<?> plays = new Array<>();
? getLast(int currentIndex){

if(currentIndex > 0)
    return plays.get(currentIndex - 1);
return plays.get(0);    

}

你需要用到棧這個數(shù)據(jù)結(jié)構(gòu) java.util.Stack，點擊下一首時把當(dāng)前這首入棧push()，上一首在將歌曲出棧pop()

private String current; //當(dāng)前歌曲

private Stack<String> stack = new Stack<>(10);

public String next(){
    if(current != null){
        stack.push(current);
    }
    current = randomSong();
    return current;
}

public String prev(){
    current = stack.pop();
    return current
}