设计模式——备忘录模式

朱雀 2022-10-01 07:53 184阅读 0赞

**备忘录模式\_保存对象状态快照**

/**
     * 快照
     * @author maikec
     * @date 2019/5/16
     */
    public class Snapshot {
        @Getter
        private String name;
        public Snapshot(String name){
            this.name = name;
        }
    }
    
    **
     * 备忘录
     * @author maikec
     * @date 2019/5/16
     */
    public class MementoHelper {
        private final List<Snapshot> snapshots = new LinkedList<>(  );
    
        /**
         * 记录快照
         * @param snapshot
         */
        public void recordSnapshot(Snapshot snapshot){
            Assert.notNull( snapshot );
    
            if (!snapshots.contains( snapshot )){
                ReentrantReadWriteLock.WriteLock writeLock = new ReentrantReadWriteLock().writeLock();
                if (writeLock.tryLock()){
                    if (snapshots.size() == 0){
                        snapshots.add( snapshot );
                    }
                    if (snapshots.size() > 0 && !snapshots.contains( snapshot )){
                        snapshots.add( snapshot );
                    }
                }
            }
        }
    
        /**
         * 获取指定索引的快照
         * @param index
         * @return
         */
        public Snapshot getSnapshot(int index){
            if (snapshots.size() < 1){
                throw new IllegalStateException( "Should Record Snapshot First" );
            }
            Assert.checkBetween( index,0,snapshots.size()-1 );
            return snapshots.get( index );
        }
    }
    复制代码

## 附录 ##

[github.com/maikec/patt…][github.com_maikec_patt] 个人GitHub设计模式案例

## 声明 ##

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转载于:https://juejin.im/post/5ce8e4ef6fb9a07ee1690446

[github.com_maikec_patt]: https://link.juejin.im?target=https%3A%2F%2Fgithub.com%2Fmaikec%2Fpattern