<分区>
我对 Java 和 JUnit 测试还很陌生，对我遇到的错误感到很困惑。错误，Null Pointer exception 作为下面的代码，我猜是因为某些东西等于 null 但我不确定为什么。
java.lang.NullPointerException
at com.nsa.y1.trafficlights.FourWayJunctionTest.PhaseOneInitiation(FourWayJunctionTest.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:114)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:57)
at org.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:66)
at org.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:51)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.internal.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
at org.gradle.internal.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
at com.sun.proxy.$Proxy2.processTestClass(Unknown Source)
at org.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:109)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
at org.gradle.internal.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
at org.gradle.internal.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:377)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745) com.nsa.y1.trafficlights.FourWayJunctionTest > PhaseOneInitiation FAILED
java.lang.NullPointerException at FourWayJunctionTest.java:47
这是测试文件:
package com.nsa.y1.trafficlights;
import org.junit.Before;
import org.junit.Test;
import static org.junit.Assert.assertEquals;
/**
* Created by c167 on 12/03/2017.
*/
public class FourWayJunctionTest {
private Light greenLight, amberLight, redLight, greenRightArrow, greenLeftArrow;
private FourLightTrafficLight turnRightTrafficLight;
boolean lightStateRed;
boolean lightStateAmber;
boolean lightStateGreen;
private TrafficLight northLeftStraight;
private FourLightTrafficLight northLeftArrow;
private FourLightTrafficLight northRightArrow;
private TrafficLight eastLeftStraight;
private TrafficLight westStraightRight;
private FourWayJunction junction = new FourWayJunction();
@Before
public void createLights() throws Exception {
greenLight = (new Light(Shape.CIRCLE, Colour.GREEN));
amberLight = (new Light(Shape.CIRCLE, Colour.AMBER));
redLight = (new Light(Shape.CIRCLE, Colour.RED));
northRightArrow = new FourLightTrafficLight();
northLeftArrow = new FourLightTrafficLight();
northLeftStraight = new TrafficLight();
eastLeftStraight = new TrafficLight();
westStraightRight = new TrafficLight();
}
@Test
public void PhaseOneInitiation() throws Exception {
createLights();
//Greenleftarrow should be on, northleft on, and eat left on. All others off.
junction.initiatePhaseOne();
assertEquals(greenLeftArrow.isOn(), true);
}
}
这是包含方法的代码:
package com.nsa.y1.trafficlights;
/**
* Created by on 13/03/2017.
*/
public class FourWayJunction extends FourLightTrafficLight{
// Evans junction recreation in cardiff
private Light greenLight, amberLight, redLight, greenRightArrow, greenLeftArrow;
private TrafficLight oppositeTrafficLight;
private FourLightTrafficLight turnRightTrafficLight;
boolean lightStateRed;
boolean lightStateAmber;
boolean lightStateGreen;
private TrafficLight northLeftStraight;
private FourLightTrafficLight northLeftArrow;
private FourLightTrafficLight northRightArrow;
private TrafficLight eastLeftStraight;
private TrafficLight westStraightRight;
public FourWayJunction() {
greenLight = (new Light(Shape.CIRCLE, Colour.GREEN));
amberLight = (new Light(Shape.CIRCLE, Colour.AMBER));
redLight = (new Light(Shape.CIRCLE, Colour.RED));
northRightArrow = new FourLightTrafficLight();
northLeftArrow = new FourLightTrafficLight();
northLeftStraight = new TrafficLight();
eastLeftStraight = new TrafficLight();
westStraightRight = new TrafficLight();
}
public void initiatePhaseOne() {
// Left arrow for buses and taxis on, north green light for left on but no right arrow.
// Also green light on for the East Traffic light.
// All others off.
westStraightRight.getRedLight().turnOn();
northRightArrow.getGreenLight().turnOff();
if (westStraightRight.getRedLight().isOn() && !northRightArrow.getGreenLight().isOn()){
northLeftArrow.getGreenLight().turnOn();
northLeftStraight.setTrafficLightOn(northLeftStraight);
eastLeftStraight.setTrafficLightOn(eastLeftStraight);
}
else {
System.out.println("Problems, traffic wil collide");
westStraightRight.setTrafficLightOff(westStraightRight);
northRightArrow.getGreenLight().turnOff();
}
}
public void initiatePhaseTwo() {
// North left straight, left arrow, and right arrow are on.
// West straight right light off.
// East Left Straight light is off.
if (!eastLeftStraight.getRedLight().isOn()) {
eastLeftStraight.setTrafficLightOff(eastLeftStraight);
northRightArrow.getGreenLight().turnOn();
}
else {
northRightArrow.getGreenLight().turnOn();
}
}
public void initiatePhaseThree() {
// All lights are off except for the EastStraightRight light.
if (northRightArrow.getGreenLight().isOn() && !northLeftStraight.getRedLight().isOn() &&
northLeftArrow.getGreenLight().isOn()) {
northRightArrow.getGreenLight().turnOff();
northLeftArrow.getGreenLight().turnOff();
northLeftStraight.setTrafficLightOff(northLeftStraight);
}
else {
eastLeftStraight.setTrafficLightOn(eastLeftStraight);
}
}
public FourLightTrafficLight getTrafficLight(FourLightTrafficLight light) {
return light;
}
}
public void setTrafficLightOn(TrafficLight trafficLight) {
trafficLight.getRedLight().turnOff();
LightPause();
trafficLight.getAmberLight().turnOn();
LightPause();
trafficLight.getGreenLight().turnOn();
}
public void setTrafficLightOff(TrafficLight trafficLight) {
trafficLight.getGreenLight().turnOff();
LightPause();
trafficLight.getGreenLight().turnOff();
trafficLight.getAmberLight().turnOn();
LightPause();
trafficLight.getRedLight().turnOn();
}
感谢您的帮助:)