Android Studio（JAVA） 编译警告:使用了未经检查或不安全的操作

在编译Android Studio（JAVA）程序时发生了如下的警告:

使用了未经检查或不安全的操作
要了解详细信息，请使用 "-Xlint:unchecked" 重新编译。

• 如何设置Android Stuido开启 "-Xlint:unchecked"

修改build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId "com.a.b.c"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        debug {
            minifyEnabled false
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.0.1'
    compile 'com.android.support:design:23.0.1'
}

增加

tasks.withType(JavaCompile) {
   options.compilerArgs << "-Xlint:unchecked"
}

修改后的如下：

apply plugin: 'com.android.application'

android {
    compileSdkVersion 23
    buildToolsVersion "23.0.1"

    defaultConfig {
        applicationId "com.a.b.c"
        minSdkVersion 15
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
        debug {
            minifyEnabled false
        }
    }

    tasks.withType(JavaCompile) {
       options.compilerArgs << "-Xlint:unchecked"
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.0.1'
    compile 'com.android.support:design:23.0.1'
}

• 警告信息的处理例子

包含-Xlint:unchecked警告的代码

final LinkedHashMap<WeakReference<Object>,WeakReference<Object>> aWeakArray = new LinkedHashMap<>();
for (Iterator iter = aWeakArray.entrySet().iterator(); iter.hasNext(); ) {
	LinkedHashMap.Entry element = (LinkedHashMap.Entry)iter.next();
	WeakReference<Object> aWeakObj = (WeakReference<Object>)element.getKey();
	WeakReference<Object> aWeakTag = (WeakReference<Object>)element.getValue();
}

消除警告后的代码如下：

final LinkedHashMap<WeakReference<Object>,WeakReference<Object>> aWeakArray = new LinkedHashMap<>();
for (Iterator<LinkedHashMap.Entry<WeakReference<Object>,WeakReference<Object>> > iter = aWeakArray.entrySet().iterator(); iter.hasNext(); ) {
	LinkedHashMap.Entry<WeakReference<Object>,WeakReference<Object>> element = iter.next();
	WeakReference<Object> aWeakObj = element.getKey();
	WeakReference<Object> aWeakTag = element.getValue();
}

同样的方法适用于"-Xlint:deprecation"。