delete() 　　是即刻删除

public boolean delete() {

SecurityManager security = System.getSecurityManager();

if (security != null) {

security.checkDelete(path);

}

if (isInvalid()) {

return false;

}

return fs.delete(this);

}

最终调用native本地方法 立即进行删除

 

deleteOnExit() 调用后，不会立即删除，会等到虚拟机正常运行结束后，才去删除

public void deleteOnExit() {

SecurityManager security = System.getSecurityManager();

if (security != null) {

security.checkDelete(path);

}

if (isInvalid()) {

return;

}

DeleteOnExitHook.add(path);

}

private DeleteOnExitHook() {}

static synchronized void add(String file) {

if(files == null) {

// DeleteOnExitHook is running. Too late to add a file

throw new IllegalStateException("Shutdown in progress");

}

files.add(file);

}

static void runHooks() {

LinkedHashSet theFiles;

synchronized (DeleteOnExitHook.class) {

theFiles = files;

files = null;

}

ArrayList toBeDeleted = new ArrayList<>(theFiles);

// reverse the list to maintain previous jdk deletion order.

// Last in first deleted.

Collections.reverse(toBeDeleted);

for (String filename : toBeDeleted) {

(new File(filename)).delete();

}

}

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