Guava工具測試

使用Preconditions校驗參數

private static void testPrecondition() {
        try {
            Preconditions.checkNotNull(null, "neme爲null");
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            String name = "mjx";
            Preconditions.checkArgument( name.equals( "blackfox" ),
                    "neme爲" + name );
        } catch (Exception e) {
            e.printStackTrace();
        }
        try {
            Preconditions.checkState( 3 < 0, "state:" + ( 3 < 0 ) );
        } catch (Exception e) {
            e.printStackTrace();
        }

        // 判斷數組使用
        int[] ints = { 1, 2, 3 };
        try {

            Preconditions.checkPositionIndex( 3, ints.length, " 越界" );
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            Preconditions.checkPositionIndexes( 0, 9, ints.length );
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            Preconditions.checkElementIndex( 9, ints.length, "越界了" );
        } catch (Exception e) {
            e.printStackTrace();
        }
}

使用Optional處理null

private static void testOptional() {
        Optional<Integer> possible = Optional.of( 6 );
        Optional<Integer> absentOpt = Optional.absent();
        Optional<Integer> NullableOpt = Optional.fromNullable( null );
        Optional<Integer> NoNullableOpt = Optional.fromNullable( 10 );
        System.out.println( "possible isPresent:" + possible.isPresent() );
        System.out.println( "possible asSet:" + possible.asSet() );
        System.out.println( "possible value:" + possible.get() );
        System.out.println( "absentOpt isPresent:" + absentOpt.isPresent() );
        System.out.println(
                "fromNullableOpt isPresent:" + NullableOpt.isPresent() );
        System.out.println(
                "NoNullableOpt isPresent:" + NoNullableOpt.isPresent() );
               
 }

參考：Guava學習筆記