//check other elements in loop } 1. 2. 3. 4. 5. 6. 7. 这会在第6行导致 NullPointerException。 因此,访问空 对象的任何字段,方法或索引会导致 NullPointerException,如上面的示例所示。避免NullPointerException的 常见方法是检查null: public void doSomething() { String result = doSomethingElse();...
AI代码解释 String somePublicNamespace="CAT";Config config=ConfigService.getConfig(somePublicNamespace);//config instance is singleton for each namespace and is never nullString someKey="someKeyFromPublicNamespace";String someDefaultValue="someDefaultValueForTheKey";String value=config.getProperty(someKe...
当monitor被占用时就处于锁定状态,线程执行monitorcenter指令时尝试获取monitor的所有权If the entry count of the monitor associated with objectref is zero, the thread enters the monitor and sets its entry count to one. The thread is then the owner of the monitor.如果monitor的进入数为0,则该线程进入...
使用Objects类的isNull方法进行空判断:Objects.isNull(object) 使用Optional类进行空判断:Optional.ofNullable(object).isPresent() 使用StringUtils类进行空判断:StringUtils.isEmpty(object) 使用Java 8 中的Optional类和Lambda表达式进行空判断:Optional.ofNullable(object).ifPresent(obj -> { // do something with obj...
String result = doSomethingElse(); if(result !=null&& result.equalsIgnoreCase("Success")){ // success } else // failure } privateString doSomethingElse(){ returnnull; } 在现实世界中,程序员发现很难识别哪些对象可以为 null。积极安全的策略可能是为每个对象检查 null。但是,这会导致大量冗余空值检查...
@Nullable iWantToDestroyEverything() { return null; } 那么这样未经检查的方法调用也会在编译期间失败: 1 iWantToDestroyEverything().something(); 也就是说,在编译时间就找出潜在的NPE问题。 对象为空的检查 不需要自己写防御性质的判断语句来处理空对象了。比如JDK7的Objects对象: ...
6)如果使用了带有null值的引用类型变量,instanceof操作将会返回false: Java代码 Integer iAmNull = null; if(iAmNull instanceof Integer){ System.out.println("iAmNull is instance of Integer"); }else{ System.out.println("iAmNull is NOT an instance of Integer"); ...
If soundcard were null, the resultingOptionalobject would be empty. Do Something If a Value Is Present Now that you have anOptionalobject, you can access the methods available to explicitly deal with the presence or absence of values. Instead of having to remember to do a null check, as fo...
else if (json instanceof JSONArray) {// if json is an Array JSONArray jsonArr = (JSONArray)json; int len = jsonArr.size(); for (int i = 0; i < len; ++i) { // TODO: do something here jsonArr.set(i, traverseJson(jsonArr.get(i))); ...
In line 2, we check for anullparameter.If the assertions are enabled, this would result in anAssertionError. Although it is a good way of asserting preconditions such as non-nullparameters,this approach has two major problems: Assertions are usually disabled in a JVM. ...