Java SoftReference类案例详解

SoftReference<String> ref = new SoftReference<String>("Hello world");

String value = ref.get();

if (value == null) {
  // 如果被GC回收了 在这里重新初始化
}
// 你的逻辑
...

public class SoftReferenceCache<K, V> {
  
  private final HashMap<K, SoftReference<V>> mCache;

  public SoftReferenceCache() {
    mCache = new HashMap<K, SoftReference<V>>();
  }
}

public void put(K key, V value) {
  mCache.put(key, new SoftReference<V>(value));
}

public V get(K key) {
  V value = null;

  SoftReference<V> reference = mCache.get(key);

  if (reference != null) {
    value = reference.get();
  }

  return value;
}

SoftReferenceCache<Integer, Person> mPersonCache = new SoftReferenceCache<Integer, Person>();

mPersonCache.put(0, new Person("Peter");
mPersonCache.put(1, new Person("Jan");
mPersonCahce.put(2, new Person("Kees");

// 去拿Jan
Person p = (Person) mPersonCache.get(1); 

import java.lang.ref.SoftReference;
import java.util.HashMap;

/**
 * SoftRefenceCache
 * @param <K> key的类型.
 * @param <V> value的类型.
 */
public class SoftReferenceCache<K, V> {
  private final HashMap<K, SoftReference<V>> mCache;

  public SoftReferenceCache() {
    mCache = new HashMap<K, SoftReference<V>>();
  }

  /**
   * 将对象放进缓存中，这个对象可以在GC发生时被回收
   * 
   * @param key key的值.
   * @param value value的值型.
   */

  public void put(K key, V value) {
    mCache.put(key, new SoftReference<V>(value));
  }

  /**
   * 从缓存中获取value
   * 
   * @param key
   *
   * @return 如果找到的话返回value，如果被回收或者压根儿没有就返* 回null
   */
   
  public V get(K key) {
    V value = null;

    SoftReference<V> reference = mCache.get(key);

    if (reference != null) {
      value = reference.get();
    }

    return value;
  }
}