Collections&Arrays

Collections:

public class Example10 {

public static void main(String[] args) {
ArrayList list=new ArrayList();
Collections.addAll(list,"C","D","E","B");
System.out.println("排序前"+list);
Collections.reverse(list);
System.out.println("翻转"+list);
Collections.sort(list);
System.out.println("自然排序"+list);
Collections.shuffle(list);
System.out.println("洗牌后"+list);
System.out.println("------------------");
ArrayList list2=new ArrayList();
Collections.addAll(list2,3,34,5,-2,49);
System.out.println("集合中元素"+list2);
System.out.println("集合中最大值"+Collections.max(list2));
System.out.println("集合中最小值"+Collections.min(list2));
Collections.replaceAll(list2,5,0);//将集合中5换为0
System.out.println("替换后的集合"+list2);
}

}

Arrays:

public class Example10 {


public static void main(String[] args) {
int[] arr={9,8,6,4,6};
System.out.println("排序前");
printArray(arr);
Arrays.sort(arr);
System.out.println("\n"+"排序后");
printArray(arr);
}
public static void printArray(int[] arr){
System.out.print("[");
for(int x=0;x<arr.length;x++){
if(x!=arr.length-1){
System.out.print(arr[x]+",");
}else{
System.out.print(arr[x]+"]");
}
}
}


}

二分法查找：

public class Example10 {public static void main(String[] args) {int[] arr={4,5,6,2,4};Arrays.sort(arr);System.out.println("排序后");for(int a:arr){System.out.print(a+" ");}int index=Arrays.binarySearch(arr,4);System.out.println("数组排序后元素是4的索引是"+index);}}