Android Studio - Program type already present: org.hamcrest.CoreMatchers
问题 I have no idea why this error exists: Program type already present: org.hamcrest.CoreMatchers Message{kind=ERROR, text=Program type already present: org.hamcrest.CoreMatchers, sources=[Unknown source file], tool name=Optional.of(D8)} My code in in the scope if dependency of build.gradle (Module: app) is: dependencies { implementation fileTree(dir: 'libs', include: ['*.jar']) implementation 'com.android.support:appcompat-v7:26.1.0' implementation 'com.android.support.constraint:constraint