1 排序操作
public class SortTest { public static void main(String[] args) { ArrayList nums = new ArrayList(); nums.add(5); nums.add(54); nums.add(15); nums.add(1); nums.add(35); // [5, 54, 15, 1, 35] System.out.println(nums); Collections.reverse(nums); // [35, 1, 15, 54, 5] System.out.println(nums); Collections.sort(nums); //[1, 5, 15, 35, 54] System.out.println(nums); //每次随机排序 Collections.shuffle(nums); System.out.println(nums); } }
2 查找、替换操作
public class SearchTest { public static void main(String[] args) { ArrayList nums = new ArrayList(); nums.add(2); nums.add(-5); nums.add(3); nums.add(0); System.out.println(nums); System.out.println(Collections.max(nums)); Collections.replaceAll(nums, 0, 1); System.out.println(nums); Collections.sort(nums); System.out.println(nums); } }
3 同步控制
public class SynchronizedTest { public static void main(String[] args) { Collection c=Collections.synchronizedCollection(new ArrayList()); List list=Collections.synchronizedList(new ArrayList()); } }
4 设置不可变集合
public class UnmodifiableTest { public static void main(String[] args) { // 创建空的、不可改变的对象 List unmodifiableList = Collections.emptyList(); Map scores = new HashMap(); scores.put("语文", 99); scores.put("数学", 98); Map unmodifiableMap = Collections.unmodifiableMap(scores); // java.lang.UnsupportedOperationException // unmodifiableList.add("1"); //unmodifiableMap.put("英语", 80); } }